Permanent magnet with improved coercive force

Abstract

The present invention relates to a method for producing a bulk magnetic material of a rare-earth metal-free permanent magnet. Specifically, the type of magnet produced by the present invention is an iron-based rare-earth-free magnet. More specifically, the magnets of the present invention belong to the hexaferrites. The present invention further relates to magnets produced by the method of the present invention, which are characterized by misaligned magnetic moments that result in improved magnetic properties such as higher coercivity.

Description

Technical Field

[0001] The present invention relates to a method for producing a bulk magnetic material of a rare-earth metal-free permanent magnet. Specifically, the type of magnet produced by the present invention is an iron-based rare-earth-free magnet. More specifically, the magnets of the present invention belong to the hexaferrites. The present invention further relates to magnets produced by the method of the present invention, which are characterized by misaligned magnetic moments that result in improved magnetic properties such as higher coercivity.

Background Art

[0002] Permanent magnets are essential components in a wide range of industrial processes, scientific research environments, and everyday life purposes. Industries such as semiconductors, automobiles, peripheral terminal devices, or large computers greatly rely on the supply of strong permanent magnets. The production of these requires both the extraction and purification of ores, as well as processes that consume high energy during magnetization.

[0003] Such strong magnets are currently mostly, in the case of rare-earth magnets such as NIB magnets, that is, a general term used for NdFeB (or Nd2Fe 14 B) type magnets. The magnetic properties of NIB magnets are highly desirable, but the high cost of rare-earth ores and environmental concerns associated with the mining and recycling of these elements have increased interest in rare-earth-free permanent magnets such as hexaferrites, which are inexpensive and abundant alternatives and may have less environmental impact.

[0004] Clearly, in the art, there is a need for an efficient method for producing rare-earth-free permanent magnets such as hexaferrites with enhanced magnetic properties using industrially feasible methods and resources.

Summary of the Invention

[0005] The present invention relates to a method for producing a rare-earth metal-free permanent magnet. Specifically, the type of magnet produced by the present invention is an iron-based rare-earth-free magnet. More specifically, the magnets of the present invention belong to the hexaferrites.

[0006] The inventors have devised a new manufacturing method that enables controlled misalignment of the magnetic moments of bulk magnetic materials, particularly hexaferrite materials. Thus, the method enables the production of a novel bulk magnetic material characterized by comprising at least two distinct magnetic portions that are not aligned with respect to each other.

[0007] Thus, one aspect of the present invention is a method for manufacturing a bulk magnetic material of hexaferrite, the bulk magnetic material comprising an aligned magnetic portion and a misaligned magnetic portion, each portion comprising or consisting of M-type strontium hexaferrite (SrFe 12 O 19 ), and the method comprising: a. providing a first iron-based oxide comprising anisotropic crystallites, the anisotropic crystallites being characterized by an average aspect ratio A / C of 5 to 500; b. providing a second iron-based oxide in the form of M-type strontium hexaferrite (SrFe 12 O 19 ), the second iron-based oxide comprising crystallites, the crystallites being characterized by an average aspect ratio A / C < 3; c. providing a certain amount of an alkaline earth metal (aem) precursor; d. mixing the first and second iron-based oxides with the alkaline earth metal (aem) precursor to obtain a final precursor mixture; e. compressing the final precursor mixture by applying a uniaxial pressure of 200 MPa to 5000 MPa, thereby inducing alignment of the first iron-based precursor to obtain a partially aligned precursor, the second iron-based precursor not being aligned by this step. f. heating the partially aligned precursor at a heating rate in the range of 10 °C / hour to 10 °C / minute to a temperature in the range of 1000 °C to 1240 °C to convert the partially aligned precursor into the bulk magnetic material of the hexaferrite; g. isolating the thus formed bulk magnetic material of hexaferrite, which comprises an aligned magnetic portion and a non-aligned magnetic portion, from the reaction mixture, each portion comprising or consisting of M-type strontium hexaferrite (SrFe 12 O 19 ); including. By utilizing the anisotropic crystallite shape of the first iron-based oxide in combination with the non-anisotropic crystallite shape of the second iron-based oxide as described below, the inventors demonstrate that it is possible without using an external magnetic field but only using pressure. Thereby, while maintaining the crystallites of the second iron-based oxide substantially unaffected, by aligning the crystallites of the first iron-based oxide in a preferred orientation, during firing, the formation of a bulk magnetic material characterized by misaligned magnetic moments is promoted, and as a result, magnetic properties such as an increase in coercivity are improved.

[0008] Accordingly, a second aspect of the present invention relates to a bulk magnetic material comprising an aligned magnetic portion and a non-aligned magnetic portion, a. the aligned magnetic portion is a hexagonal platelet of hexaferrite, b. the non-aligned magnetic portion is a hexagonal crystallite of hexaferrite, the aligned magnetic portion is uniformly aligned, the non-aligned magnetic portion is not uniformly aligned, nor aligned with respect to the aligned magnetic portion, and the aligned and non-aligned magnetic portions of hexaferrite comprise or consist of M-type strontium hexaferrite (SrFe 12 O 19 ).

[0009] As a result of the enhanced magnetic properties obtained by the controlled misalignment of magnetic moments in the bulk magnetic material of the present invention, the present disclosure demonstrates broad utility as an alternative to other ferrite materials or NIB rare earth magnets. Aspects of the present invention are that the bulk magnetic material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0010] A further aspect of the present invention generally relates to the bulk magnetic materials described hereinbelow for use as magnetic components in various devices such as electric motors.

[0011] Although not as important as the anisotropic form, it is also preferred that the first iron-based oxide essentially interact non-ferromagnetically. When the first iron-based oxide interacts non-ferromagnetically, the risk of magnetic domain short-circuiting is eliminated during the fabrication steps of the hexaferrite permanent magnet. Otherwise, in this step, heating above the Curie temperature of the precursor, for example, by application of spark plasma sintering (SPS), or alternatively application of a large magnetic field to block ferromagnetic interactions, would be required. Since both of these are undesirable in terms of scale-up to industrial scale, it is beneficial to eliminate them.

[0012] Thus, by utilizing the non-ferromagnetism in the first iron-based oxide in combination with both anisotropic and non-anisotropic crystallites described herein, it is possible to fabricate bulk magnetic materials with improved magnetic properties, such as rare earth-free magnets having improved coercivity at industrially relevant scales and costs.

[0013] Another advantage of the manufacturing method claimed in this specification is that there are substantially no size limitations on the magnets produced. When an external magnetic field is required, the size of the magnet is limited by the magnitude of the homogeneous magnetic field that can be generated, which is a serious limiting factor for the industrial scalability of very large magnets. However, in the case of the method claimed in this specification, the magnets can be produced by simple cold pressing (i.e., compression at room temperature), without the need for a large magnetic field, and as a result, the only limiting feature with respect to size is the appropriate press tool, making it more easily implementable on an industrial scale.

Brief Description of the Drawings

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[0015] One aspect of the present invention relates to a method for manufacturing a bulk magnetic material of hexaferrite, the bulk magnetic material comprising aligned magnetic portions and non-aligned magnetic portions, the method comprising: a. providing a first iron-based oxide comprising anisotropic crystallites, wherein the anisotropic crystallites have an average aspect ratio A / C of 5 to 500; b. providing a second iron-based oxide comprising crystallites, wherein the crystallites have an average aspect ratio A / C < 3; c. providing a quantity of alkaline earth metal (aem) precursor; d. mixing the first and second iron-based oxides with the alkaline earth metal (aem) precursor to obtain a final precursor mixture; e. compressing the final precursor mixture by applying a uniaxial pressure of 200 MPa to 5000 MPa, thereby inducing alignment of the first iron-based precursor to obtain a partially aligned precursor, wherein the second iron-based precursor is not aligned by this step; f. heating the partially aligned precursor at a heating rate in the range of 10 °C / hour to 10 °C / second to a temperature in the range of 1000 °C to 1250 °C to convert the partially aligned precursor into the bulk magnetic material of the hexaferrite; g. isolating the thus formed bulk magnetic material of the hexaferrite, which includes an aligned magnetic portion and a non-aligned magnetic portion, from the reaction mixture. It includes. In one embodiment of the present disclosure, the hexaferrite produced by the described method is selected from the group consisting of M-type hexaferrite, X-type hexaferrite, and W-type hexaferrite, and preferably, it is M-type hexaferrite. Furthermore, in one embodiment of the present disclosure, the M-type hexaferrite is M-type strontium hexaferrite (SrFe 12 O 19 ), M-type barium hexaferrite (BaFe 12 O 19 ), M-type calcium hexaferrite (CaFe 12 O 19 ) and substituents thereof, and preferably, it is M-type strontium hexaferrite (SrFe 12 O 19 ).

[0016] All chemical structures and atomic structures of M-type, W-type, and X-type hexaferrites are well-known to those skilled in the art without further explanation. In one embodiment, each of the aligned and non-aligned portions of the bulk magnetic material is M-type strontium hexaferrite (SrFe12 O 19 ) such as consisting of M-type strontium hexaferrite (SrFe 12 O 19 ) is preferably included.

[0017] Aspect ratio: This is understood as the ratio of the length (A direction) of the crystals of the precursor to the height (C direction) of the same crystals (see also FIGS. 2a and 2b). The difference between A and C gives the precursor its unique properties in that it promotes the alignment of crystallites in the final magnet. The aspect ratio can be determined by standard methods known in the art such as X-ray powder diffraction (XRD), or preferably by transmission electron microscopy (TEM).

[0018] Anisotropic crystallites: By this, the crystallites are not spherical, i.e., the crystallites are in the shape of small plates, plate-like shapes, needles or needle-like shapes, so that when compressed, substantial fragments of the crystallites such as all the crystallites will align in the same direction due to the difference in aspect ratio (see also the aspect ratio above).

[0019] The crystallite aspect ratio for the first iron-based oxide material disclosed herein, etc., is defined by the average A / C ratio, and in one embodiment of the present disclosure, it needs to be 5 or more for fitting as anisotropic crystallites. The difference in aspect ratio between the first iron-based oxide and the second iron-based oxide is extremely important for the present disclosure, as this depends on the preferred orientation of the iron-based oxide with a large average A / C ratio compared to the iron-based oxide with a low average A / C ratio in the synthesis of a hexaferrite permanent magnet with misaligned magnetic moments, preferably a strontium hexaferrite permanent magnet.

[0020] In one embodiment, the first iron-based oxide is characterized in that the average aspect ratio A / C is 5 to 500. In one embodiment, the average aspect ratio A / C of the first iron-based oxide is 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100, for example 100 to 125, for example 125 to 150, for example 150 to 200, for example 200 to 400, for example 400 to 500.

[0021] In one embodiment of the present disclosure, the first iron-based oxide is characterized in that the average aspect ratio A / C is 5 to 100. In one embodiment, the average aspect ratio A / C of the first iron-based oxide is 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100.

[0022] In one embodiment of the present disclosure, the first iron-based oxide is characterized in that the average aspect ratio A / C is 5 to 50, for example 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50.

[0023] In one embodiment, the second iron-based oxide is characterized in that the average aspect ratio A / C ≤ 3. In one embodiment, the average aspect ratio A / C of the second iron-based oxide is 3.0 to 1.0, for example 3.0 to 2.5, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.0.

[0024] In one embodiment, the average aspect ratio A / C of the second iron-based oxide is less than 3.0, for example less than 2.8, for example less than 2.7, for example less than 2.6, for example 2.5 to 1.0, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.0.

[0025] In one embodiment, the average aspect ratio A / C of the second iron-based oxide is not more than 3.0.

[0026] In one embodiment of the present disclosure, the first iron-based oxide includes anisotropic crystallites having a platelet or platelet-like form.

[0027] In one embodiment of the present disclosure, the first iron-based oxide includes anisotropic crystallites having a needle or needle-like form.

[0028] Similar to a deck of playing cards, when dropped on the floor, most cards will lie flat on top of each other, but only a few cards can be expected to land on their narrow sides (in the case of platelet-like anisotropic crystallites). Similarly, in the case of needles, when a needle is dropped on the floor, the long part of the needle will lie flat parallel to the floor, but it is very rare for the needle to stand vertically (in the case of needle-like anisotropic crystallites).

[0029] Aligning mainly all the crystallites in a magnetic sample in the same direction is also aligning the magnetic moment of the sample in the same direction. Figuratively speaking, this is equivalent to aligning all the magnetic field lines of small individual magnets in the same direction to achieve a synergistic effect and generate a larger unidirectional magnetic field. Therefore, a magnet configured in this way can have excellent magnetic properties compared to an unaligned version of the same magnet, as demonstrated in Examples 5, 6, and 8.

[0030] The criterion for evaluating the magnetic properties of a material is to examine the hysteresis behavior of the magnet (see Figure 1). The important parameters that govern the macroscopic magnetic properties of a material are the remanent magnetization (M r ), saturation magnetization (M s ), coercive field (H c ), and maximum energy product (BH) max ), and all of these can be extracted from the magnetic hysteresis loop. However, in some applications such as electric motors, the coercive field (H c ) is generally regarded as being very important.

[0031] When measuring magnetic hysteresis, the sample is exposed to an external magnetic field that increases from zero. Then, as the external magnetic field increases, the magnetization of the sample increases. When the magnetization of the sample no longer increases even when a larger magnetic field is applied, the magnetization is said to be saturated. This value is called the saturation magnetization (M s ). Then, the external magnetic field is decreased back to zero to demagnetize the sample. As a result, the magnetization decreases to some extent. If the magnetization is not zero at zero applied magnetic field (i.e., H = 0), this value corresponds to the remanent magnetization (M r ). The sign of the external magnetic field is changed, and figuratively speaking, the magnetic field increases in the opposite direction. Since the magnetization of the magnet at zero applied magnetic field is non-zero, a negative magnetic field needs to be applied to make the magnetization zero. The value of this magnetic field is called the coercive force field (H c ).

[0032] The alignment of the moments within the sample also affects the shape of the magnetic hysteresis curve, as illustrated in FIG. 1. A highly aligned magnet has a hysteresis curve that is positively perpendicular, where the events of magnetization and demagnetization occur very abruptly when the coercive force field value is reached. When the alignment of the sample is less, the shape of the hysteresis loop becomes smoother. Similarly, the magnetization and demagnetization events become more gradual.

[0033] The larger the crystallite aspect ratio of the precursor of the present disclosure (see FIGS. 2a and 2b), the higher the likelihood that the crystallites will stack in a preferred orientation, which in turn promotes the improvement of magnetic properties.

[0034] Following the above analogy, it can be considered that the crystallites of the second iron-based oxide, characterized by an average aspect ratio A / C < 3, are substantially spherical and / or isotropic crystallites that are not significantly affected by the surrounding arrangement. Therefore, a mixture of playing cards and spheres dropped on the floor still results in most, if not all, of the playing cards landing flat on the ground or on top of or under the spheres. Some may be found angled around the spheres, but mainly the flat surfaces are aligned with the floor. If the spheres are considered to have a certain magnetic moment and the playing cards are considered to have another magnetic moment, a situation occurs where the magnetic moments of the playing cards are uniformly aligned in the same direction, while the magnetic moments of the spheres are randomly oriented.

[0035] In one embodiment of the present disclosure, the anisotropic crystallites of the first iron-based oxide are characterized in that C ranges from 2 to 200 nm, for example 2 to 10 nm, for example 10 to 15 nm, for example 15 to 20 nm, for example 20 to 30 nm, for example 30 to 50 nm, for example 50 to 80 nm, for example 80 to 110 nm, for example 110 to 140 nm, for example 140 to 170 nm, for example 170 to 200 nm.

[0036] In one embodiment of the present disclosure, the anisotropic crystallites of the first iron-based oxide are characterized in that A ranges from 10 to 1000 nm, for example 10 to 20 nm, for example 20 to 30 nm, for example 30 to 40 nm, for example 40 to 50 nm, for example 50 to 75 nm, for example 75 to 100 nm, for example 100 to 125 nm, for example 125 to 250 nm, for example 250 to 500 nm, for example 500 to 1000 nm.

[0037] In one embodiment of the present disclosure, the first iron-based oxide is goethite, hematite, 6-line ferrihydrite, and hexaferrite, for example, M-type hexaferrite, preferably M-type strontium hexaferrite (SrFe 12 O 19 ) or M-type barium hexaferrite (BaFe 12 O 19) or M-type calcium hexaferrite (CaFe 12 O 19 ), selected from the group consisting of W-type hexaferrite, and X-type hexaferrite.

[0038] In one embodiment of the present disclosure, the first iron-based oxide is a ferromagnetic iron-based oxide that interacts ferromagnetically, such as an iron-based oxide that is ferromagnetic under ambient conditions.

[0039] In one embodiment of the present disclosure, the first iron-based oxide is an antiferromagnetic iron-based oxide that interacts antiferromagnetically, such as an iron-based oxide that is antiferromagnetic under ambient conditions.

[0040] Antiferromagnetic: Thus, it is understood as a chemical substance that has unpaired electrons and no permanent magnetism is observed within the temperature range related to the present disclosure, preferably at room temperature (i.e., the magnetization is approximately zero under zero applied external magnetic field). The terms "antiferromagnetic", "antiferromagnetically interacting", and "non-magnetic" can be used interchangeably in this specification. By the same logic, "ferromagnetic", "magnetic", and "ferromagnetically interacting" can be used interchangeably in this specification and can refer to a chemical substance having non-zero magnetization under a non-zero applied external field.

[0041] In one embodiment of the present disclosure, the first iron-based oxide interacts antiferromagnetically and is selected from goethite, hematite, or 6-line ferrihydrite, preferably goethite.

[0042] In one embodiment of the present disclosure, the first iron-based oxide is ferromagnetic and is selected from M-type hexaferrites such as M-type strontium hexaferrite (SrFe 12 O 19 ), M-type barium hexaferrite (BaFe 12 O 19 ), or M-type calcium hexaferrite (CaFe 12 O 19 ), W-type hexaferrite, or X-type hexaferrite.

[0043] The first iron-based oxide contains large fragments of crystallites having a platelet or needle-like morphology defined by an average A / C aspect ratio greater than 5, and can be converted into a hexaferrite permanent magnet by either a one-step process by spark plasma sintering (SPS), or a two-step process in which a crystalline powder is first compressed into a pellet by applying uniaxial pressure and then fired at a temperature of 1000°C to 1250°C.

[0044] When the first iron-based oxide is non-ferromagnetic, the anisotropic crystallites of the first iron-based oxide can be aligned in a preferred direction solely by applying pressure, and then a permanent magnetic material can be produced by firing the pressed and partially aligned precursor. However, when the first iron-based oxide is inherently ferromagnetic, figuratively speaking, the magnetic interaction between individual anisotropic crystallites "locks" the crystallites in place and prevents alignment using only pressure. In such a situation, it is necessary to apply a large external magnetic field or heat the sample above the Curie temperature of the ferromagnetic crystallites to disrupt the magnetic interaction. The most efficient approach to this is spark plasma sintering (SPS), which can achieve compression and heating (sintering) in one step.

[0045] In one embodiment of the present disclosure, the method steps of compression and heating described herein may be performed sequentially by a first step of cold compression and a second step of firing, or the steps may be performed simultaneously, such as by spark plasma sintering (SPS).

[0046] In one embodiment of the present disclosure, the second iron-based oxide is selected from the group consisting of M-type strontium hexaferrite (SrFe 12 O 19 ), hematite, M-type barium hexaferrite (BaFe 12 O 19 ), M-type calcium hexaferrite (CaFe 12 O 19 ), goethite, W-type hexaferrite, and X-type hexaferrite.

[0047] In one embodiment of the present disclosure, the average aspect ratio A / C of the second iron-based oxide is from 3.0 to 1.0, for example, from 3.0 to 2.5, for example, from 2.5 to 2.0, for example, from 2.0 to 1.5, for example, from 1.5 to 1.0, preferably from 2.0 to 1.0.

[0048] In one embodiment, the average aspect ratio A / C of the second iron-based oxide is less than 3.0, for example, less than 2.8, for example, less than 2.7, for example, less than 2.6, for example, from 2.5 to 1.0, for example, from 2.5 to 2.0, for example, from 2.0 to 1.5, for example, from 1.5 to 1.0, preferably from 2.0 to 1.0.

[0049] In one embodiment, the average aspect ratio A / C of the second iron-based oxide is not more than 3.0.

[0050] In one embodiment of the present disclosure, the first iron-based oxide and the second iron-based oxide are mixed in a weight ratio of 99:1 to 50:50.

[0051] In one embodiment of the present disclosure, the mixing ratio of the first iron-based oxide and the second iron-based oxide is in the range of 99:1 to 50:50 by weight, for example, 99:1 to 95:5, for example, 95:5 to 90:10, for example, 90:10 to 85:15, for example, 85:15 to 80:20, for example, 80:20 to 75:25, for example, 75:25 to 70:30, for example, 70:30 to 65:35, for example, 65:35 to 60:40, for example, 60:40 to 55:45, for example, 55:45 to 50:50.

[0052] In one embodiment of the present disclosure, the first iron-based oxide is goethite and the second iron-based oxide is strontium hexaferrite.

[0053] In one embodiment of the present disclosure, the first iron-based oxide is goethite and the second iron-based oxide is strontium hexaferrite, and the mixing ratio of the first iron-based oxide and the second iron-based oxide is from 90:10 to 70:30 by weight, for example, from 85:15 to 75:25 by weight, for example, 80:20 by weight.

[0054] In one embodiment of the present disclosure, the first iron-based oxide is goethite and the second iron-based oxide is hematite.

[0055] In one embodiment of the present disclosure, the first iron-based oxide is goethite and the second iron-based oxide is hematite, and the mixing ratio of the first iron-based oxide and the second iron-based oxide is a weight ratio of 90:10 to 70:30, for example, a weight ratio of 85:15 to 75:25, for example, a weight ratio of 80:20.

[0056] In one embodiment of the present disclosure, the first iron-based oxide is 6-line ferrihydrite and the second iron-based oxide is strontium hexaferrite.

[0057] In one embodiment of the present disclosure, the first iron-based oxide is 6-line ferrihydrite and the second iron-based oxide is strontium hexaferrite, and the mixing ratio of the first iron-based oxide and the second iron-based oxide is a weight ratio of 90:10 to 70:30, for example, a weight ratio of 85:15 to 75:25, for example, a weight ratio of 80:20.

[0058] In one embodiment of the present disclosure, the first iron-based oxide is 6-line ferrihydrite and the second iron-based oxide is hematite.

[0059] In one embodiment of the present disclosure, the first iron-based oxide is 6-line ferrihydrite and the second iron-based oxide is hematite, and the mixing ratio of the first iron-based oxide and the second iron-based oxide is a weight ratio of 90:10 to 70:30, for example, a weight ratio of 85:15 to 75:25, for example, a weight ratio of 80:20.

[0060] In one embodiment of the present disclosure, the alkaline earth metal (aem) precursor is provided in an amount to obtain an Fe / aem molar ratio in the range of 8 to 14, for example, 8 to 9, for example, 9 to 10, for example, 10 to 10.5, for example, 10.5 to 11, for example, 11 to 11.5, for example, 11.5 to 12, for example, 12 to 13, for example, 13 to 14.

[0061] In one embodiment of the present disclosure, the alkaline earth metal (aem) precursor contains an alkaline earth metal selected from the group consisting of Sr, Ba, Ca, Mg, Be, and Ra, preferably contains Sr or Ba or Ca, and most preferably contains Sr.

[0062] In one embodiment of the present disclosure, the alkaline earth metal (aem) precursor contains Sr and is selected as one or more from the group consisting of SrCO3, SrO, Sr(OH)2, SrCl2, Sr(NO3)2, SrSO4, Sr(OAc)2, Sr3(PO4)2, and their hydrates, and is preferably SrCO3.

[0063] In one embodiment of the present disclosure, the alkaline earth metal (aem) precursor contains Ba and is selected as one or more from the group consisting of BaCO3, BaO, Ba(OH)2, BaCl2, Ba(NO3)2, BaSO4, Ba(OAc)2, Ba3(PO4)2, and their hydrates, and is preferably BaCO3.

[0064] In one embodiment of the present disclosure, the alkaline earth metal (aem) precursor contains Ca and is selected as one or more from the group consisting of CaCO3, CaO, Ca(OH)2, CaCl2, Ca(NO3)2, CaSO4, Ca(OAc)2, Ca3(PO4)2, and their hydrates, and is preferably CaCO3.

[0065] In one embodiment of the present disclosure, the applied uniaxial pressure is 200 MPa to 5000 MPa, for example 200 MPa to 500 MPa, for example 500 MPa to 650 MPa, for example 650 MPa to 800 MPa, for example 800 MPa to 1000 MPa, for example 1000 MPa to 1200 MPa, for example 1200 MPa to 1500 MPa, for example 1500 MPa to 2000 MPa, for example 2000 MPa to 3000 MPa, for example 3000 MPa to 4000 MPa, for example 4000 MPa to 5000 MPa. Preferably, the applied uniaxial pressure is 800 MPa to 1500 MPa, for example 800 MPa to 1000 MPa, for example 1000 MPa to 1200 MPa, for example 1200 MPa to 1500 MPa.

[0066] In one embodiment of the present disclosure, the uniaxial pressure applied is 800 MPa to 1200 MPa, preferably 1000 MPa to 1200 MPa.

[0067] In one embodiment of the present disclosure, the temperature is 1000 °C to 1250 °C, such as 1050 °C to 1075 °C, such as 1075 °C to 1100 °C, such as 1100 °C to 1125 °C, such as 1125 °C to 1150 °C, such as 1150 °C to 1175 °C, such as 1175 °C to 1200 °C, such as 1200 °C to 1220 °C, 1220 °C to 1240 °C, such as 1240 °C to 1250 °C.

[0068] In one embodiment of the present disclosure, the temperature is 1000 °C to 1240 °C, such as 1075 °C to 1240 °C, such as 1100 °C to 1200 °C.

[0069] In one embodiment of the present disclosure, the heating rate is 10 °C / hour to 10 °C / minute, such as 10 °C / hour to 30 °C / hour, such as 30 °C / hour to 45 °C / hour, such as 45 °C / hour to 1 °C / minute, such as 1 °C / minute to 2 °C / minute, such as 2 °C / minute to 5 °C / minute, such as 5 °C / minute to 10 °C / minute, preferably 5 °C / minute.

[0070] In one embodiment of the present disclosure, the heating rate is 10 °C / hour to 10 °C / second, such as 10 °C / hour to 30 °C / hour, such as 30 °C / hour to 45 °C / hour, such as 45 °C / hour to 1 °C / minute, such as 1 °C / minute to 2 °C / minute, such as 2 °C / minute to 5 °C / minute, such as 5 °C / minute to 10 °C / minute, such as 10 °C / minute to 30 °C / minute, such as 30 °C / minute to 1 °C / second, such as 1 °C / minute to 5 °C / second, such as 5 °C / second to 10 °C / second.

[0071] Another aspect of the present invention relates to a bulk magnetic material obtainable by the method described above herein.

[0072] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein includes aligned magnetic portions and non-aligned magnetic portions. a. The aligned magnetic portions are hexagonal platelets of hexaferrite, b. The unaligned magnetic portions are hexagonal crystallites of hexaferrite. In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein is characterized in that the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the unaligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0073] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein is further characterized by a coercive force in the range of 300 kA / m to 1000 kA / m.

[0074] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein is characterized in that the aligned magnetic portions constitute 50 wt% to 99 wt% of the bulk portion of the magnetic material.

[0075] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein is characterized in that the unaligned magnetic portions constitute 1 wt% to 50 wt% of the bulk portion of the magnetic material.

[0076] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein has aligned and unaligned magnetic portions of hexaferrite that are M-type strontium hexaferrite (SrFe 12 O 19 ).

[0077] In one embodiment of the present disclosure, the bulk magnetic material obtainable by the method described above herein is characterized by not containing rare earth metals (including oxides or salts of rare earth metals) such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0078] Another aspect of the present invention relates to a bulk magnetic material comprising an aligned magnetic portion and a non-aligned magnetic portion. a. The aligned magnetic portion is a hexagonal platelet of hexaferrite. b. The non-aligned magnetic portion is a hexagonal crystallite of hexaferrite. The aligned magnetic portions are uniformly aligned, and the non-aligned magnetic portions are neither uniformly aligned nor aligned with respect to the aligned magnetic portions.

[0079] Aligned and non-aligned portions: Thus, the alignment of the magnetic moments of the individual magnetic portions is understood not only with respect to each other but also with respect to the surface normal of the bulk magnetic material of the present invention. As used herein, "alignment" and "texture" may be used interchangeably. Since the orientation of the magnetic moment is related to the spatial orientation of the crystallites, alignment may also indirectly refer to the alignment of the crystallites.

[0080] As a result of the anisotropy of the crystallites contained in the first iron-based oxide, during the production of the bulk magnetic material, the crystallites of the first iron-based oxide, and thus the magnetic moments, are preferentially aligned in a uniform direction, and the magnetic moments preferentially coincide with the surface normal of the bulk magnetic material of the present invention, thereby constituting a magnetic portion aligned within the scope of the present invention. By the same logic, the crystallites of the second iron-based oxide described herein, which are characterized by a low aspect ratio (less than the average aspect ratio A / C3), do not align because the anisotropy of the crystallites is not sufficient to achieve this. That is, the crystallites are isotropic. Therefore, both the crystallites and the magnetic moments contained in the second iron-based oxide are randomly oriented with respect to both the easy magnetization axes of the bulk magnetic material of the present invention, and optionally also randomly oriented with respect to the surface normal of the same bulk magnetic material, thereby constituting a non-aligned magnetic portion.

[0081] As used herein, the phrase "easy magnetization axis" should be construed as the direction in space that is energetically favorable for an anisotropic magnetic material to be magnetized. In other words, the easy magnetization axis is the energetically favorable direction of spontaneous magnetization in a magnetically anisotropic material. In comparison, in a magnetically isotropic material, all directions are equally favorable for magnetization, so there is no easy axis. This phrase is well known to those skilled in the art.

[0082] As used herein, the phrase "surface normal" should be construed as the vector perpendicular to the surface at a given point. This phrase is well known to those skilled in the art.

[0083] In one embodiment of the present disclosure, the aligned magnetic portion is uniformly aligned with respect to the bulk magnetic material, and the non-aligned magnetic portion is randomly oriented with respect to the easy magnetization axis of the bulk magnetic material.

[0084] In one embodiment of the present disclosure, the aligned magnetic portion is uniformly aligned with respect to the bulk magnetic material, the easy magnetization axis of the aligned magnetic portion coincides within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portion is randomly oriented with respect to the easy magnetization axis of the bulk magnetic material.

[0085] In one embodiment of the present disclosure, the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the surface normal of the bulk magnetic material.

[0086] In one embodiment of the present disclosure, the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0087] In one embodiment of the present disclosure, the easy magnetization axis of the aligned magnetic portions coincides within ±25° of the surface normal of the bulk magnetic material, for example within ±24°, for example within ±23°, for example within ±22°, for example within ±21°, for example within ±20°, for example within ±19°, for example within ±18°, for example within ±17°, for example within ±16°, for example within ±15°, for example within ±14°, for example within ±13°, for example within ±12°, for example within ±11°, for example within ±10°, for example within ±9°, for example within ±8°, for example within ±7°, for example within ±6°, for example within ±5°.

[0088] In one embodiment, the easy magnetization axis of the aligned magnetic portions coincides within ±20° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0089] In one embodiment, the easy magnetization axis of the aligned magnetic portions coincides within ±15° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0090] In one embodiment, the easy magnetization axis of the aligned magnetic portions coincides within ±10° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0091] In one embodiment, the easy magnetization axes of the aligned magnetic portions coincide within ±5° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0092] In one embodiment of the present disclosure, the texture and degree of alignment and the composition distribution of the aligned and non-aligned portions (or phases) in the bulk magnetic material may be determined by diffraction methods known to those skilled in the art. In one embodiment, such a diffraction method can be 2D X-ray diffraction. In another embodiment, such a diffraction method may be electron backscatter diffraction (EBSD). EBSD can be performed in accordance with ISO2417:2009.

[0093] From the collected 2D diffraction data, a two-phase model is used to account for the aligned and non-aligned portions. Both phases are exemplarily fixed as M-type strontium hexaferrite (SrFe 12 O 19 ), and the unit cell and atomic positions are fixed for the two phases. The difference between the two phases needs to be alignment, which may also be called texture. Phase 1 based on anisotropic platelets or acicular crystallites is textured, while phase 2 based on spherical or non-anisotropic crystallites is not textured. Refinement of the measurement data returns the phase fractions of the two phases. The resulting phase fractions correlate with the amounts of the first iron-based oxide and the second iron-based oxide (e.g., anisotropic goethite and spherical hematite) used in the fabrication process, respectively. In phase 1, it is necessary to give a weight fraction of goethite of ±5 wt%, while the non-textured sample needs to be equal to the amount of spherical hematite used ±5 wt%. In an example where 15 wt% of spherical hematite is added to anisotropic goethite, the weight fraction of the non-aligned phase needs to be 10-20 wt%. Instead, when 25 wt% of spherical hematite is added, the resulting weight fraction of the non-aligned phase needs to be 20-30 wt%.

[0094] In one embodiment of the present disclosure, the aligned and non-aligned magnetic portions of the hexaferrite are selected individually from the group consisting of M-type hexaferrites such as M-type strontium hexaferrite (SrFe 12 O 19 ), M-type barium hexaferrite (BaFe 12 O 19 ), or M-type calcium hexaferrite (CaFe 12 O 19 ), W-type hexaferrite, and X-type hexaferrite. In one embodiment, the aligned and non-aligned magnetic portions of the hexaferrite are M-type strontium hexaferrite (SrFe 12 O 19 ).

[0095] In one embodiment of the present disclosure, the aligned magnetic portion constitutes 50 wt% to 99 wt%, for example 50 wt% to 60 wt%, for example 60 wt% to 70 wt%, for example 70 wt% to 75 wt%, for example 75 wt% to 80 wt%, for example 80 wt% to 85 wt%, for example 85 wt% to 90 wt%, for example 90 wt% to 95 wt%, for example 95 wt% to 99 wt% of the bulk magnetic material.

[0096] In one embodiment of the present disclosure, the aligned magnetic portion constitutes 70 wt% to 90 wt%.

[0097] In one embodiment of the present disclosure, the aligned magnetic portion constitutes 75 wt% to 85 wt%.

[0098] In one embodiment of the present disclosure, the aligned magnetic portion constitutes 80 wt% to 90 wt%.

[0099] In one embodiment of the present disclosure, the non-aligned magnetic portion constitutes 1 wt% to 50 wt%, for example 1 wt% to 5 wt%, for example 5 wt% to 10 wt%, for example 10 wt% to 15 wt%, for example 15 wt% to 20 wt%, for example 20 wt% to 25 wt%, for example 25 wt% to 30 wt%, for example 30 wt% to 40 wt%, for example 40 wt% to 50 wt% of the bulk magnetic material.

[0100] In one embodiment of the present disclosure, the non-magnetic portion constitutes 15 wt% to 25 wt%.

[0101] In one embodiment of the present disclosure, the aligned magnetic portion constitutes 10 wt% to 20 wt%.

[0102] In one embodiment of the present disclosure, the bulk magnetic material further has a coercivity in the range of 200 kA / m to 1000 kA / m, such as 200 kA / m to 250 kA / m, such as 250 kA / m to 300 kA / m, such as 300 kA / m to 350 kA / m, such as 350 kA / m to 375 kA / m, such as 375 kA / m to 400 kA / m, such as 400 kA / m to 425 kA / m, such as 425 kA / m to 450 kA / m, such as 450 kA / m to 500 kA / m, such as 500 kA / m to 750 kA / m, such as 750 kA / m to 1000 kA / m.

[0103] In one embodiment of the present disclosure, the bulk magnetic material further has a coercivity in the range of 300 kA / m to 1000 kA / m, such as 300 kA / m to 350 kA / m, such as 350 kA / m to 375 kA / m, such as 375 kA / m to 400 kA / m, such as 400 kA / m to 425 kA / m, such as 425 kA / m to 450 kA / m, such as 450 kA / m to 500 kA / m, such as 500 kA / m to 750 kA / m, such as 750 kA / m to 1000 kA / m.

[0104] In one embodiment of the present disclosure, the bulk magnetic material is further characterized by a coercivity in the range of 350 kA / m to 450 kA / m.

[0105] In one embodiment of the present disclosure, the aligned magnetic portion further has an average aspect ratio A / C in the range of 5 to 10, such as 10 to 15, such as 15 to 20, such as 20 to 30, such as 30 to 40, such as 40 to 50, such as 50 to 75, such as 75 to 100, such as 100 to 125, such as 125 to 150, such as 150 to 200, such as 200 to 400, such as 400 to 500.

[0106] In one embodiment of the present disclosure, the misaligned magnetic portion is further characterized by an average aspect ratio A / C in the range of 3.0 to 1.0, such as 3.0 to 2.5, such as 2.5 to 2.0, such as 2.0 to 1.5, such as 1.5 to 1.0, preferably 2.0 to 1.0.

[0107] In one embodiment, the average aspect ratio A / C of the misaligned magnetic portion is less than 3.0, such as less than 2.8, such as less than 2.7, such as less than 2.6, such as 2.5 to 1.0, such as 2.5 to 2.0, such as 2.0 to 1.5, such as 1.5 to 1.0, preferably 2.0 to 1.0.

[0108] In one embodiment, the average aspect ratio A / C of the misaligned magnetic portion is not more than 3.0.

[0109] In one embodiment of the present disclosure, the aligned magnetic portion and the misaligned magnetic portion are magnetically coupled, such as in a two-phase coupled magnetic system.

[0110] In one embodiment of the present disclosure, the bulk magnetic material described herein does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0111] As a result of the enhanced magnetic properties obtained by the controlled misalignment of the magnetic moments in the bulk magnetic material of the present invention, the present disclosure demonstrates broad utility as an alternative to other ferrite materials or NIB rare earth magnets.

[0112] A further aspect of the present invention generally relates to the bulk magnetic material described above herein, or a bulk magnetic material obtained by the method described above herein for use as a magnetic component within a device.

[0113] In one embodiment, such a device may be an electric motor. Other possible devices known to those skilled in the art may be (non-limiting) selected from the group consisting of a storage device, a generator, an audio device, a magnetic imaging scanner, a magnetic brake, a linear motor, an electrodynamic bearing, and a magnetic toy.

Example

[0114] Example 1: Preparation of partially misaligned SrFe 12 O 19 nanoparticles from a mixture with solid salt matrix (SSM) SrFe 12 O 19 hexaferrite magnets.

[0115] 1.1 - Preparation of anisotropic goethite nanoparticles.

[0116] Rod-shaped α-FeOOH nanocrystals were synthesized using hydrothermal synthesis. A 40 mL solution of 1 M Fe(NO3)3·9H2O was prepared, and 20 mL of 8.0 M NaOH solution was added dropwise to the nitrate-containing solution under constant magnetic stirring to form a transparent red solution and form a gel-like compound. The amount of NaOH was adjusted so that the ratio of Fe 3+ :OH - was 1:4. The precursor gel could be stirred for 1 hour. The precursor gel was transferred to a 5 L polypropylene plastic bottle and placed in an oven at 70 °C for 18 hours.

[0117] 1.1a - Alternative preparation of anisotropic goethite nanoparticles.

[0118] Rod-shaped α-FeOOH nanocrystals were synthesized using hydrothermal synthesis. A 40 mL solution of 1 M Fe(NO3)3·9H2O was prepared, and 20 mL of 8.0 M NaOH solution was added dropwise to the nitrate-containing solution under constant magnetic stirring to form a transparent red solution and form a gel-like compound. The amount of NaOH was adjusted so that the ratio of Fe 3+ :OH -It was adjusted so that the ratio became 1:4. The precursor gel could be stirred for 1 hour. The precursor gel was transferred to a 5 L polypropylene plastic bottle and placed in an oven at 70 °C for 18 hours. Particle sizes extracted from TEM analysis of the sample: A = 116 nm, C = 15 nm, A / C = 7.7 1.1b - Preparation of anisotropic hematite nanoparticles.

[0119] When the rod-shaped α-FeOOH nanocrystals prepared according to 1.1a above are placed in an oven and heated at 350 °C for 30 minutes, dehydration of goethite begins and anisotropic hematite nanocrystals are formed. Particle sizes extracted from TEM analysis of the sample: A = 116 nm, C = 15 nm (A / C = 7.7).

[0120] 1.2 - Preparation of anisotropic 6-line ferrihydrite (SLF) nanoparticles.

[0121] 6-line ferrihydrite (SLF) nanocrystals were synthesized by using a hydrothermal synthesis route. 25 mL of a 3.0 M Fe(NO3)3·9H2O solution and 7 mL of a 0.75 M Sr(NO3)2 solution were prepared, and 38 mL of 8.0 M NaOH (technical grade, Sigma Aldrich, purity >98%) was added dropwise to the nitrate-containing precursor solution under constant magnetic stirring to form a transparent solution into a gel-like compound. The Fe / Sr ratio was fixed at 8, and [OH - to [NO3 - was maintained at 1.29. Subsequently, the precursor gel could be stirred for about 3 hours. Next, the precursor gel was transferred to a 175 mL autoclave and placed inside the oven at 200 °C for 5 hours. Crystallite sizes extracted from X-ray powder diffraction: A = 16 nm, C = 5.2 nm (A / C = 3.1).

[0122] 1.3 - Preparation of SrFe 12 O 19 nanoparticles using NaCl solid salt matrix (SSM) synthesis.

[0123] SrFe synthesized with NaCl solid salt matrix (SSM) 12 O 19The nanocrystals were prepared by mixing 4.7 g of SrCl₂·6H₂O dissolved in 17 mL of distilled H₂O with 55 g of FeCl₃·6H₂O (Sigma Aldrich technical grade with purity > 98%) dissolved in 100 mL of distilled H₂O. The [Fe 3+ :[Sr 2+ molar ratio used was 11.5:1, which is an excess of Sr 2+ compared to the stoichiometric ratio of 12:1. Subsequently, 32 mL of 1 M Na₂CO₃ solution (Chem-Solution GmbH, 99.98% purity) was added to the metal ion solution under constant stirring, and the [Na + :[Cl - molar ratio was equal to 1. Finally, 9 mL of 5 M citric acid (> 99% purity, Sigma Aldrich) was added and the solution was stirred until the mixture was completely homogeneous. The molar ratio of citric acid to Na₂CO₃ was 1.5. The solution was dried overnight at 120 °C in a convection oven to form a porous gel. The gel was crushed in a mortar and placed in a layer about 2 mm thick in the convection oven at 450 °C for 1 hour to burn off the organic residues. Then, the precursor was calcined at 790 °C for 1 hour and cooled to room temperature.

[0124] The product was washed and centrifuged once with 100 mL of 4 M HNO₃ and four times with distilled water to remove NaCl and potential SrCO₃ (formed by the excess Sr 2+ ). Finally, the SrFe 12 O 19 powder was dried at 90 °C in a convection oven. Crystallite size extracted from X-ray powder diffraction: A = 60 nm, C = 25 nm (A / C = 2.4). Particle size extracted from TEM analysis of the sample: A = 62 nm, C = 28 nm (A / C = 2.2).

[0125] 1.4 - High coercivity SrFe 12 O 19 magnets with partially aligned g - site / SrFe 12 O 19 SSM or hematite / SrFe 12 O 19 SSM or SLF / SrFe 12 O19 Preparation of SSM particle precursors.

[0126] The goethite (GO) anisotropic nanoparticles according to Example 1.1 or 1.1a, or the hematite anisotropic nanoparticles according to Example 1.1b, or the 6-line ferrihydrite (SLF) nanoparticles according to Example 1.2 were mixed with the SSM-synthesized SrFe 12 O 19 particles of Example 1.3 to obtain a homogeneous mixture. The selected ratios were 100% / 0%, 85% / 15%, 80% / 20%, and 75% / 25% by weight. The composition of each sample was analyzed by X-ray fluorescence spectrometer. This was done to determine the concentration of Sr 2+ in the mixture. The Fe / Sr ratio was adjusted to 10 by the addition of SrCO3 and confirmed by energy-dispersive X-ray fluorescence spectrometry using a NEX CG Rigaku spectrometer.

[0127] 1.5 - High coercivity SrFe 12 O 19 GO / SrFe 12 O 19 SSM or hematite / SrFe 12 O 19 SSM or SLF / SrFe 12 O 19 Low-temperature compression and firing of SSM particle precursors.

[0128] Compression of the homogeneous powder mixture of Example 1.4 into bulk magnets was carried out by a conventional uniaxial press. Approximately 0.08 g of either the GO / SSM SrFe 12 O 19 or SLF / SSM SrFe 12 O 19 mixture was used for the production of each pellet and loaded into a 6 mm die. A pressure of up to approximately 1.2 GPa was applied to each pellet for 5 minutes. The powders of each ratio specified in Example 1.4 were sintered at approximately 1150 °C, 1190 °C, and 1250 °C for 30 minutes. The heating ramp used was 5 °C / min and the sample was placed in a carbolite tube furnace.

[0129] Example 2: Hydrothermally autoclaved (AC) SrFe 12 O 19 nanoparticles and solid salt matrix (SSM) synthesized SrFe 12 O 19 Preparation of partially misaligned SrFe12O19 hexaferrite magnets from a mixture with nanoparticles. 2.1 - Synthesis of hydrothermally autoclaved (AC) SrFe 12 O 19 synthesis.

[0130] 5 mL of 1.0 M Sr(NO3)2 and 30 mL of 1.0 M Fe(NO3)3·9H2O (≥98% purity, Sigma Aldrich) dissolved in deionized water were used to synthesize SrFe 12 O 19 nanocrystals. The metal solutions were mixed at a molar ratio of [Fe 3+ :[Sr 2+ of 6. Water was added, and then the metal solutions were mixed. 9.4 mL of 16 M NaOH was slowly added dropwise to the metal solutions under constant magnetic stirring to form a homogeneous brown precipitate using a [OH - :[NO3 - molar ratio of 1.5. The Sr 2+ concentration in the final precursor was 0.1 M. The precipitate was prepared directly in a 170 mL Teflon-lined steel autoclave. The autoclave was placed in a preheated carborundum convection box furnace set at 240 °C for 3 hours. After that, the autoclave was cooled to room temperature, the product was washed with 20 mL of 4 M HNO3, then washed three times in deionized water, and dried at 90 °C. Particle sizes extracted from TEM analysis of the sample: A = 260 nm, C = 32 nm (A / C = 8.2).

[0131] 2.2 - Mixing of powders.

[0132] SSM synthesized SrFe 12 O 19The nanoparticle powder was prepared as described above under Example 1.2. The AC and SSM synthesized crystallites were mixed in two different ways. A) Dry mixing: The crystallites were dry mixed manually using a mortar and pestle. B) Wet mixing: The as-prepared SSM powder was added to the autoclave precipitate.

[0133] 2.2.1 - Dry mixing: Three different mass ratios between AC and SSM were prepared (AC:SSM 75:25, 50:50, and 25:75). For each mixture, a total of 0.6 g of powder was used. The sample names are DM75, DM50, and DM25 according to the amount of AC prepared powder in the sample (75 wt% AC for the DM75 sample, etc.).

[0134] 2.2.2 - Wet mixing: The as-prepared SSM powder was added to the autoclave. The Fe 3+ and Sr 2+ solutions were made in one batch and divided into three Teflon-lined steel autoclaves. NaOH was added to the individual autoclaves. Then, the SSM prepared powder was added to the autoclave insert and mixed with the precipitate using a glass rod. In particular, since the SSM crystallites are highly magnetic, magnetic stirring cannot be used. Three samples were prepared at an AC:SSM ratio of 75:25, 50:50, or 25:75 calculated from the theoretical AC synthesis yield assuming a 100% yield with respect to the Fe 3+ content. The samples were named WM75, WM50, and WM25 according to the theoretical amount of AC prepared powder in the sample (75 wt% AC for the WM75 sample, etc.).

[0135] 2.3 - Spark plasma sintering (SPS) of the AC / SSM mixed powder.

[0136] The powder samples described in Examples 2.2.1 and 2.2.2 were compressed into high-density pellets using a spark plasma sintering (SPS) press (SPS Syntex Inc., Dr. Sinter Lab (trademark) series). Approximately 0.45 g of powder was filled into a graphite matrix with an inner diameter of 8 mm and sintered at 950 °C for 5 minutes at 100 MPa. The resulting pellets had a typical thickness of about 1.2 mm and were indicated in the sample naming by the P-prefix to show the processing by SPS.

[0137] Example 3: Characterization of partially misaligned SrFe12O19 hexaferrite magnets. 3.1 - Transmission electron microscopy Transmission electron microscopy (TEM) was recorded with a FEI TALOS F200 (200V) (S) TEM microscope. Representative TEM images of the goethite nanoparticles of Example 1.1 are shown in Fig. 4A, and representative TEM images of the SSM SrFe 12 O 19 nanoparticles are shown in Fig. 4B.

[0138] 3.2 - Magnetic properties A Quantum Design Physical Properties Measurement System (PPMS) equipped with a vibrating sample magnetometer (VSM) was used to access the powders as well as the pellets. A cylindrical near-zero background brass holder was used together with a quartz rod to hold the sample in place during measurement. The hysteresis curves were measured at 300 K in an externally applied magnetic field cycling between ±3 T. The frequency was set to 40 Hz and the magnetic field sweep rate was set to 50 Oe / second. The saturation magnetization M S was determined based on the approach law to saturation.

[0139] Goethite / SSM SrFe 12 O 19The magnetic hysteresis loop of a permanent magnet produced by cold compression at a weight ratio of 85:15 of (referred to as GO / SSM) and subsequent firing can be seen in Figure 7. Hysteresis loops have also been measured for other weight ratios and mixtures as shown by the extracted magnetic parameters seen in Tables 1 - 4 below, but including them at this point would be redundant.

[0140]

Table 1

Table 2

Table 3

Table 4

[0141]

Table 5

[0142] AC / SSM SrFe 12 O 19 For the samples, the hysteresis loops can be seen in Figures 5 and 6 for the SPS - treated samples of dry mixing and wet mixing respectively. The extracted magnetic parameters are shown in Table 6 below.

[0143]

Table 6

[0144] 3.3 - Diffraction data 3.3.1 - Characterization of misaligned permanent magnets of SrFe by 2D diffraction data 12 O 19 The sample is aligned such that the surface normal is rotated by 45° with respect to the incident beam (ω = 45°). Figure 8 schematically shows the measurement principle used for the characterization of misalignment by 2D diffraction data. A randomly aligned sample has a complete diffraction cone observable by a 2D detector. This is because in a randomly oriented sample, there are always some lattice planes that satisfy the Laue condition of Q = H. Here, Q is the scattering vector (Q = q in -q out where q in and q out are the incident and outgoing wave vectors, respectively), H is the reciprocal lattice vector given by H = ha* + kb* + lc*, hkl are the Miller indices, and a*, b*, and c* are the reciprocal unit lattice vectors. Due to the preferred crystallographic alignment (or texture) of the crystallites within the sample, the Laue condition is not always satisfied, and as can be seen schematically in Figure 8 (left), the diffraction cone is interrupted. Next, as illustrated in Figure 8 (right), the diffraction cone is azimuthally integrated into 5° slices and stacked as a function of 2θ. Here, a model can be constructed to refine the data, and in order to describe the azimuthally binned data, it is necessary to introduce a partial alignment (or texture) with the refined model.

[0145] Figure 9 shows an enlargement of the azimuthally integrated data collected using synchrotron radiation (Petra-III, beamline P02.1 at the Deutsches Elektronen-Synchrotron DESY in Hamburg, Germany, using an X-ray beam of 60 keV). The investigated samples of SrFe 12 O 19 were prepared by compressing the following loose powders.

[0146] A) Spherical hematite (α-Fe2O3, diameter of about 100 nm) and strontium carbonate (SrCO3), B) Anisotropic goethite (α-FeOOH, acicular crystallites with a length of about 100 nm and a thickness of 5 nm) containing strontium carbonate (SrCO3) and spherical hematite (α-Fe2O3, diameter of about 100 nm), C) Anisotropic goethite (α-FeOOH, needle-shaped crystallites approximately 100 nm in length and 5 nm in thickness) and strontium carbonate (SrCO3).

[0147] For all samples, the powders were mixed by grinding in a mortar for 15 minutes and then poured into a press matrix, which was cold-compressed at a pressure of up to 1.2 GPa for 5 minutes. The resulting pellets were then sintered at 1200 °C. The samples were rotated 45° with respect to the incident X-ray beam, and the diffraction signals were collected with a 2D detector.

[0148] By utilizing the morphological differences, it is possible to create a non-aligned sample by using only spherical (or isotropic) shaped crystallites. It is possible to fabricate a highly textured sample by using only needle-shaped or platelet-shaped crystallites. By mixing spherical and needle / platelet-shaped crystallites, it is possible to introduce misaligned components into an aligned matrix. Figure 9B shows the azimuthal integration of a sample in which the matrix components are misaligned.

[0149] 3.3.2 - Evaluation of texture degree based on 2D diffraction data: To model the data, a two-phase model was used, considering the aligned and misaligned parts. Both phases are M-type strontium hexaferrite (SrFe 12 O 19) is fixed as, and the unit cell and atomic positions are fixed for the two phases. The difference between the two phases needs to be an alignment, which may also be called a texture. Phase 1 based on anisotropic platelets or acicular crystallites is textured, while phase 2 based on spherical or non - anisotropic crystallites is not textured. The refinement of the measurement data returns the phase fractions of the two phases. The obtained phase fractions correspond to the amounts of the first iron - based oxide and the second iron - based oxide (e.g., anisotropic goethite and spherical hematite) respectively used in the fabrication process. In phase 1, it is necessary to give a weight fraction of goethite ±5 wt%, while the non - textured sample needs to be equal to the amount of spherical hematite used ±5 wt%. In the example where 15 wt% of spherical hematite is added to anisotropic goethite, the weight fraction of the non - aligned phase needs to be 10 - 20 wt%. Instead, when 25 wt% of spherical hematite is added, the weight fraction of the obtained non - aligned phase needs to be 20 - 30 wt%.

[0150] 3.3.3 - Electron Backscatter Diffraction (EBSD) Electron Backscatter Diffraction (EBSD) is a scanning electron microscope (SEM) - based microstructure - crystal property evaluation technique commonly used in the study of crystalline or polycrystalline materials. The electron beam is rastered across the sample, and the diffraction signals at each individual point are collected by a dedicated EBSD detector. A Laue diffraction pattern is collected at each point, and by indexing the pattern, it is possible to determine the crystal phase and the orientation of the crystallites. EBSD can be carried out in accordance with ISO2417:2009.

[0151] Highly aligned SrFe prepared from AC100 powder by SPS compression 12 O 19 An example of the SEM / EBSD image of the sample is shown in Fig. 10. Fig. 10A is the orientation of individual particles obtained by indexing individual diffraction spots, and Fig. 10B is an inverse pole figure showing that most of the crystallites are aligned along the (001) direction, i.e., the easy axis of the system.

[0152] In the bulk magnetic hexaferrite of the present invention containing partially misaligned magnetic moments, for example, in 75% to 85% of the sample, most of the sample is aligned within ±15° of the easy axis, and the misalignment ratio constitutes 15% to 25% in a random orientation. A part of the randomly oriented sample is within a 30° window around the easy axis - thus, the total number of randomly aligned non - anisotropic crystallites is 13.5% to 22.5%. In the EBSD image, this is observed as crystallites of a color deviating from red. In the inverse pole figure, this means that 13.5% to 22.5% of the volume is misaligned with respect to the (001) easy axis.

[0153] Item 1. A bulk magnetic material comprising an aligned magnetic portion and a misaligned magnetic portion, a. The aligned magnetic portion is a hexagonal platelet of hexaferrite, b. The misaligned magnetic portion is a hexagonal crystallite of hexaferrite, The aligned magnetic portion is uniformly aligned, and the misaligned magnetic portion is neither uniformly nor aligned with respect to the aligned magnetic portion. The bulk magnetic material.

[0154] 2. The bulk magnetic material according to item 1, wherein the aligned magnetic portion is uniformly aligned with respect to the bulk magnetic material, and the misaligned magnetic portion is randomly oriented with respect to the easy magnetization axis of the bulk magnetic material.

[0155] 3. The bulk magnetic material according to any one of items 1 to 2, wherein the aligned magnetic portion is uniformly aligned with respect to the bulk magnetic material, the easy magnetization axis of the aligned magnetic portion coincides within ±25° of the surface normal of the bulk magnetic material, and the misaligned magnetic portion is randomly oriented with respect to the easy magnetization axis of the bulk magnetic material.

[0156] 4. The aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the surface normal of the bulk magnetic material. The bulk magnetic material according to any one of items 1 to 3.

[0157] 5. The aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material. The bulk magnetic material according to any one of items 1 to 4.

[0158] 6. The easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, for example, within ±24°, for example, within ±23°, for example, within ±22°, for example, within ±21°, for example, within ±20°, for example, within ±19°, for example, within ±18°, for example, within ±17°, for example, within ±16°, for example, within ±15°, for example, within ±14°, for example, within ±13°, for example, within ±12°, for example, within ±11°, for example, within ±10°, for example, within ±9°, for example, within ±8°, for example, within ±7°, for example, within ±6°, for example, within ±5°. The bulk magnetic material according to any one of items 3 to 5.

[0159] 7. The aligned and non-aligned magnetic portions of the hexaferrite are individually selected from the group consisting of M-type hexaferrites such as M-type strontium hexaferrite (SrFe 12 O 19 ), M-type barium hexaferrite (BaFe 12 O 19 ), or M-type calcium hexaferrite (CaFe 12 O 19 ), W-type hexaferrite, and X-type hexaferrite. The bulk magnetic material according to any one of items 1 to 6.

[0160] 8. The aligned and non-aligned magnetic portions of the hexaferrite are M-type strontium hexaferrite (SrFe 12 O 19 ), and the bulk magnetic material according to any one of items 1 to 7.

[0161] 9. The aligned magnetic portion constitutes 50 wt% to 99 wt%, for example 50 wt% to 60 wt%, for example 60 wt% to 70 wt%, for example 70 wt% to 75 wt%, for example 75 wt% to 80 wt%, for example 80 wt% to 85 wt%, for example 85 wt% to 90 wt%, for example 90 wt% to 95 wt%, for example 95 wt% to 99 wt% of the bulk portion of the magnetic material, and the bulk magnetic material according to any one of items 1 to 8.

[0162] 10. The aligned magnetic portion constitutes 1 wt% to 50 wt%, for example 1 wt% to 5 wt%, for example 5 wt% to 10 wt%, for example 10 wt% to 15 wt%, for example 15 wt% to 20 wt%, for example 20 wt% to 25 wt%, for example 25 wt% to 30 wt%, for example 30 wt% to 40 wt%, for example 40 wt% to 50 wt% of the bulk portion of the magnetic material, and the bulk magnetic material according to any one of items 1 to 9.

[0163] 11. The bulk magnetic material according to any one of items 1 to 10, further characterized by a coercive force in the range of 200 kA / m to 1000 kA / m.

[0164] 12. The coercive force of the bulk magnetic material is 200 kA / m to 250 kA / m, for example 250 kA / m to 300 kA / m, for example 300 kA / m to 350 kA / m, for example 350 kA / m to 375 kA / m, for example 375 kA / m to 400 kA / m, for example 400 kA / m to 425 kA / m, for example 425 kA / mm to 450 kA / m, for example 450 kA / m to 500 kA / m, for example 500 kA / m to 750 kA / m, for example 750 kA / m to 1000 kA / m, and the bulk magnetic material according to item 11.

[0165] 13. The bulk magnetic material according to any one of items 1 to 12, wherein the aligned magnetic portion further has an average aspect ratio A / C in the range of 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100, for example 100 to 125, for example 125 to 150, for example 150 to 200, for example 200 to 400, for example 400 to 500.

[0166] 14. The bulk magnetic material according to any one of items 1 to 13, wherein the non-aligned magnetic portion further has an average aspect ratio A / C in the range of 3.0 to 1.0, for example 3.0 to 2.5, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.0.

[0167] 15. The bulk magnetic material according to any one of items 1 to 14, wherein the material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0168] 16. A method for manufacturing a bulk magnetic material of hexaferrite, wherein the bulk magnetic material includes an aligned magnetic portion and a non-aligned magnetic portion, and the method includes: a. providing a first iron-based oxide containing anisotropic crystallites, wherein the anisotropic crystallites are characterized in that the average aspect ratio A / C is 5 to 500, and the step of providing; b. providing a second iron-based oxide containing crystallites, wherein the crystallites are characterized in that the average aspect ratio A / C < 3, and the step of providing; c. providing a certain amount of alkaline earth metal (aem) precursor; d. Mixing the first and second iron-based oxides with the alkaline earth metal (aem) precursor to obtain a final precursor mixture; e. Compressing the final precursor mixture by applying a uniaxial pressure of 200 MPa to 5000 MPa, thereby inducing alignment of the first iron-based precursor and obtaining a partially aligned precursor, wherein the second iron-based precursor is not aligned in this step; f. Heating the partially aligned precursor at a heating rate in the range of 10 °C / hour to 10 °C / second to a temperature in the range of 1000 °C to 1250 °C to convert the partially aligned precursor into the bulk magnetic material of the hexaferrite; g. Isolating the thus formed bulk magnetic material of the hexaferrite, which comprises an aligned magnetic part and a non-aligned magnetic part, from the reaction mixture; including. 17. The method according to item 16, wherein the hexaferrite is selected from the group consisting of M-type hexaferrite, X-type hexaferrite, and W-type hexaferrite.

[0169] 18. The method according to any one of items 16 to 17, wherein the hexaferrite is M-type hexaferrite.

[0170] 19. The M-type hexaferrite is selected from the group consisting of M-type strontium hexaferrite (SrFe 12 O 19 ), M-type barium hexaferrite (BaFe 12 O 19 ), M-type calcium hexaferrite (CaFe 12 O 19 ) and its substituents. The method according to any one of items 17 to 18.

[0171] 20. The method according to any one of items 16 to 19, wherein the hexaferrite does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0172] 21. The method according to any one of items 16 to 20, wherein the first iron-based oxide is goethite, hematite, 6-line ferrihydrite, and hexaferrite, for example, M-type hexaferrite, preferably M-type strontium hexaferrite (SrFe 12 O 19 ) or M-type barium hexaferrite (BaFe 12 O 19 ) or M-type calcium hexaferrite (CaFe 12 O 19 ), W-type hexaferrite, and X-type hexaferrite, and is selected from the group consisting of them.

[0173] 22. The method according to any one of items 16 to 21, wherein the first iron-based oxide interacts non-ferromagnetically, such as being non-ferromagnetic under ambient conditions.

[0174] 23. The method according to any one of items 16 to 22, wherein the first iron-based oxide interacts non-ferromagnetically and is selected from goethite, hematite, or 6-line ferrihydrite, and is preferably goethite.

[0175] 24. The method according to any one of items 16 to 23, wherein the average aspect ratio A / C of the first iron-based oxide is 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100, for example 100 to 125, for example 125 to 150, for example 150 to 200, for example 200 to 400, for example 400 to 500.

[0176] 25. The method according to any one of items 16 to 24, wherein the second iron-based oxide is selected from the group consisting of M-type strontium hexaferrite (SrFe 12 O 19 ), hematite, M-type barium hexaferrite (BaFe 12 O 19 ), M-type calcium hexaferrite (CaFe 12 O 19 ), goethite, W-type hexaferrite, and X-type hexaferrite.

[0177] 26. The method according to any one of items 16 to 25, wherein the average aspect ratio A / C of the second iron-based oxide is 3.0 to 1.0, for example 3.0 to 2.5, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.0.

[0178] 27. The method according to any one of items 16 to 26, wherein the first iron-based oxide and the second iron-based oxide are mixed in a weight ratio range of 99:1 to 50:50.

[0179] 28. The method according to any one of items 16 to 27, wherein the mixing ratio is in the range of 99:1 to 50:50 by weight, for example 99:1 to 95:5, for example 95:5 to 90:10, for example 90:10 to 85:15, for example 85:15 to 80:20, for example 80:20 to 75:25, for example 75:25 to 70:30, for example 70:30 to 65:35, for example 65:35 to 60:40, for example 60:40 to 55:45, for example 55:45 to 50:50.

[0180] 29. The method according to any one of items 16 to 28, wherein the alkaline earth metal (aem) precursor is provided in an amount to obtain an Fe / aem molar ratio in the range of 8 to 14, such as 8 to 9, such as 9 to 10, such as 10 to 10.5, such as 10.5 to 11, such as 11 to 11.5, such as 11.5 to 12, such as 12 to 13, such as 13 to 14.

[0181] 30. The method according to any one of items 16 to 29, wherein the alkaline earth metal (aem) precursor contains an alkaline earth metal selected from the group consisting of Sr, Ba, Ca, Mg, Be, and Ra.

[0182] 31. The method according to any one of items 16 to 30, wherein the alkaline earth metal (aem) is selected from the group consisting of Sr and Ba, preferably Sr.

[0183] 32. The method according to any one of items 16 to 31, wherein the alkaline earth metal (aem) precursor is selected as one or more from the group consisting of SrCO3, SrO, Sr(OH)2, SrCl2, Sr(NO3)2, SrSO4, Sr(OAc)2, Sr3(PO4)2, and their hydrates.

[0184] 33. The method according to any one of items 16 to 32, wherein the alkaline earth metal (aem) precursor is selected as one or more from the group consisting of BaCO3, BaO, Ba(OH)2, BaCl2, Ba(NO3)2, BaSO4, Ba(OAc)2, Ba3(PO4)2, and their hydrates.

[0185] 34. The method according to any one of items 16 to 33, wherein the applied uniaxial pressure is 200 MPa to 5000 MPa, for example, 200 MPa to 500 MPa, for example, 500 MPa to 650 MPa, for example, 650 MPa to 800 MPa, for example, 800 MPa to 1000 MPa, for example, 1000 MPa to 1200 MPa, for example, 1200 MPa to 1500 MPa, for example, 1500 MPa to 2000 MPa, for example, 2000 MPa to 3000 MPa, for example, 3000 MPa to 4000 MPa, for example, 4000 MPa to 5000 MPa. 35. The method according to any one of items 16 to 34, wherein the temperature is 1000 °C to 1250 °C, for example, 1050 °C to 1075 °C, for example, 1075 °C to 1100 °C, for example, 1100 °C to 1125 °C, for example, 1125 °C to 1150 °C, for example, 1150 °C to 1175 °C, for example, 1175 °C to 1200 °C, for example, 1200 °C to 1220 °C, for example, 1220 °C to 1240 °C, for example, 1240 °C to 1250 °C.

[0186] 36. The method according to any one of items 16 to 35, wherein the heating rate is 10 °C / hour to 10 °C / minute, for example, 10 °C / hour to 30 °C / hour, for example, 30 °C / hour to 45 °C / hour, for example, 45 °C / hour to 1 °C / minute, for example, 1 °C / minute to 2 °C / minute, for example, 2 °C / minute to 5 °C / minute, for example, 5 °C / minute to 10 °C / minute.

[0187] 37. A bulk magnetic material obtainable by the method according to any one of items 16 to 36.

[0188] 38. The bulk magnetic material according to item 37, wherein the bulk magnetic material includes aligned magnetic portions and non-aligned magnetic portions. a. The aligned magnetic portions are hexagonal platelets of hexaferrite. b. The non-aligned magnetic portions are hexagonal crystallites of hexaferrite. The bulk magnetic material according to item 37. 39. The aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material. The bulk magnetic material according to any one of items 37 to 38.

[0189] 40. The bulk magnetic material according to any one of items 37 to 39, further characterized by a coercive force in the range of 200 kA / m to 1000 kA / m.

[0190] 41. The aligned magnetic portions constitute 50 wt% to 99 wt% of the bulk portion of the magnetic material. The bulk magnetic material according to any one of items 37 to 40.

[0191] 42. The non-aligned magnetic portions constitute 1 wt% to 50 wt% of the bulk portion of the magnetic material. The bulk magnetic material according to any one of items 37 to 41.

[0192] 43. The aligned and non-aligned magnetic portions of the hexaferrite are M-type strontium hexaferrite (SrFe 12 O 19 ). The bulk magnetic material according to any one of items 37 to 42.

[0193] 44. The material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y). The bulk magnetic material according to any one of items 37 to 43.

[0194] 45. Use of the bulk magnetic material according to any one of items 1 to 15 or 37 to 44, or the bulk magnetic material obtained by the method defined in any one of items 16 to 36, as a magnetic component in a device.

[0195] 46. The use method according to item 45, wherein the device is an electric motor.

[0196] Item 2 1. A bulk magnetic material comprising an aligned magnetic portion and a non-aligned magnetic portion, a. The aligned magnetic portion is a hexagonal platelet of hexaferrite, b. The non-aligned magnetic portion is a hexagonal crystal of hexaferrite, The aligned magnetic portions are uniformly aligned, and the non-aligned magnetic portions are neither uniformly nor aligned with respect to the aligned magnetic portions. The bulk magnetic material.

[0197] 2. The bulk magnetic material according to item 1, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axes of the aligned magnetic portions coincide within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

[0198] 3. The bulk magnetic material according to any one of items 1 to 2, wherein the aligned and non-aligned magnetic portions of hexaferrite are M-type strontium hexaferrite (SrFe 12 O 19 )).

[0199] 4. The bulk magnetic material according to any one of items 1 to 3, wherein the aligned magnetic portions constitute 70% to 90% by weight of the bulk portion of the magnetic material. 5. The bulk magnetic material according to any one of items 1 to 4, further characterized by a coercive force in the range of 200 kA / m to 1000 kA / m.

[0200] 6. The bulk magnetic material according to item 5, wherein the coercive force of the bulk magnetic material is 350 kA / m to 450 kA / m.

[0201] 7. The bulk magnetic material according to any one of items 1 to 6, wherein the material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0202] 8. A method for manufacturing a bulk magnetic material of hexaferrite, wherein the bulk magnetic material includes an aligned magnetic portion and a non-aligned magnetic portion, and the method includes: a. Providing a first iron-based oxide containing anisotropic crystallites, wherein the anisotropic crystallites are characterized in that the average aspect ratio A / C is 5 to 500, and the providing step; b. Providing a second iron-based oxide containing crystallites, wherein the crystallites are characterized in that the average aspect ratio A / C < 3, and the providing step; c. Providing a certain amount of an alkaline earth metal (aem) precursor; d. Mixing the first and second iron-based oxides with the alkaline earth metal (aem) precursor to obtain a final precursor mixture; e. Compressing the final precursor mixture by applying a uniaxial pressure of 200 MPa to 5000 MPa, thereby inducing alignment of the first iron-based precursor to obtain a partially aligned precursor, wherein the second iron-based precursor is not aligned in this step, and the obtaining step; f. heating the partially aligned precursor at a heating rate in the range of 10 °C / hour to 10 °C / second to a temperature in the range of 1000 °C to 1250 °C to convert the partially aligned precursor into the bulk magnetic material of the hexaferrite; g. isolating the thus formed bulk magnetic material of the hexaferrite, which comprises an aligned magnetic portion and a non-aligned magnetic portion, from the reaction mixture; The method comprising the above steps. 9. The method according to item 8, further characterized in that the hexaferrite is M-type strontium hexaferrite (SrFe 12 O 19 ), the alkaline earth metal (aem) precursor is SrCO3, and the hexaferrite does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

[0203] 10. The method according to any one of items 8 to 9, wherein the first iron-based oxide is selected from the group consisting of goethite, hematite, 6-line ferrihydrite, and hexaferrite, such as M-type hexaferrite, preferably M-type strontium hexaferrite (SrFe 12 O 19 ) or M-type barium hexaferrite (BaFe 12 O 19 ) or M-type calcium hexaferrite (CaFe 12 O 19 ), W-type hexaferrite, and X-type hexaferrite.

[0204] 11. The first iron-based oxide interacts non-ferromagnetically and is selected from goethite, hematite, or 6-line ferrihydrite, preferably goethite, and the average aspect ratio A / C of the first iron-based oxide is 5 to 100, such as 5 to 10, such as 10 to 15, such as 15 to 20, such as 20 to 30, such as 30 to 40, such as 40 to 50, such as 50 to 75, such as 75 to 100. The method according to any one of items 8 to 10.

[0205] 12. The second iron-based oxide is M-type strontium hexaferrite (SrFe 12 O 19 ), hematite, M-type barium hexaferrite (BaFe 12 O 19 ), M-type calcium hexaferrite (CaFe 12 O 19 ), goethite, W-type hexaferrite, and X-type hexaferrite, and the average aspect ratio A / C of the second iron-based oxide is 3.0 to 1.0, such as 3.0 to 2.5, such as 2.5 to 2.0, such as 2.0 to 1.5, such as 1.5 to 1.0, preferably 2.0 to 1.0. The method according to any one of items 8 to 11.

[0206] 13. The mixing ratio of the first iron-based oxide and the second iron-based oxide is in the range of 99:1 to 50:50 by weight, preferably, for example, 90:10 to 70:30. The method according to any one of items 8 to 12.

[0207] 14. A bulk magnetic material obtainable by the method according to any one of items 8 to 13.

[0208] 15. Use of the bulk magnetic material according to any one of items 1 to 8 or 14 as a magnetic component in a device such as an electric motor, or the bulk magnetic material obtained by the method defined in any one of items 8 to 13.

Claims

1. A bulk magnetic material comprising aligned magnetic portions and non-aligned magnetic portions, a. The aligned magnetic portions are hexagonal platelets of hexaferrite, b. The non-aligned magnetic portions are hexagonal crystallites of hexaferrite, The aligned magnetic portions are uniformly aligned, and the unaligned magnetic portions are not uniformly aligned or aligned with respect to the aligned magnetic portions. The aligned magnetic portions and the unaligned magnetic portions of the hexaferrite are M-type strontium hexaferrite (SrFe １２ O １９ ) and contain or consist of The bulk magnetic material.

2. The bulk magnetic material according to claim 1, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy axis of magnetization of the bulk magnetic material.

3. The bulk magnetic material according to any one of claims 1 to 2, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy axis of magnetization of the aligned magnetic portions coincides within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy axis of magnetization of the bulk magnetic material.

4. The bulk magnetic material according to any one of claims 1 to 3, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy axis of magnetization of the aligned magnetic portions coincides within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the surface normal of the bulk magnetic material.

5. The bulk magnetic material according to any one of claims 1 to 4, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy axis of magnetization of the aligned magnetic portions coincides within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy axis of magnetization and / or the surface normal of the bulk magnetic material.

6. The bulk magnetic material according to any one of claims 3 to 5, wherein the easy axis of magnetization of the aligned magnetic portions coincides within ±25°, for example within ±24°, for example within ±23°, for example within ±22°, for example within ±21°, for example within ±20°, for example within ±19°, for example within ±18°, for example within ±17°, for example within ±16°, for example within ±15°, for example within ±14°, for example within ±13°, for example within ±12°, for example within ±11°, for example within ±10°, for example within ±9°, for example within ±8°, for example within ±7°, for example within ±6°, for example within ±5° of the surface normal of the bulk magnetic material.

7. The aligned magnetic portion constitutes 50 wt% to 99 wt%, for example 50 wt% to 60 wt%, for example 60 wt% to 70 wt%, for example 70 wt% to 75 wt%, for example 75 wt% to 80 wt%, for example 80 wt% to 85 wt%, for example 85 wt% to 90 wt%, for example 90 wt% to 95 wt%, for example 95 wt% to 99 wt% of the bulk portion of the magnetic material, the bulk magnetic material according to any one of claims 1 to 6.

8. The non-aligned magnetic portion constitutes 1 wt% to 50 wt%, for example 1 wt% to 5 wt%, for example 5 wt% to 10 wt%, for example 10 wt% to 15 wt%, for example 15 wt% to 20 wt%, for example 20 wt% to 25 wt%, for example 25 wt% to 30 wt%, for example 30 wt% to 40 wt%, for example 40 wt% to 50 wt% of the bulk portion of the magnetic material, the bulk magnetic material according to any one of claims 1 to 7.

9. The alignment is measured by electron backscatter diffraction (EBSD), for example in accordance with ISO 2417:2009, the bulk magnetic material according to any one of claims 1 to 8.

10. When measured at 300 K in an externally applied magnetic field that cycles between ±3 T using a vibrating sample magnetometer (VSM) operating at a frequency of 40 Hz and 50 Oe / sec, it is further characterized by a coercive force in the range of 300 kA / m to 1000 kA / m, the bulk magnetic material according to any one of claims 1 to 9.

11. The coercive force of the bulk magnetic material, when measured at 300 K in an externally applied magnetic field that cycles between ±3 T using a vibrating sample magnetometer (VSM) operating at a frequency of 40 Hz and 50 Oe / sec, is 300 kA / m to 350 kA / m, for example 350 kA / m to 375 kA / m, for example 375 kA / m to 400 kA / m, for example 400 kA / m to 425 kA / m, for example 425 kA / m to 450 kA / m, for example 450 kA / m to 500 kA / m, for example 500 kA / m to 750 kA / m, for example 750 kA / m to 1000 kA / m, the bulk magnetic material according to claim 10.

12. The bulk magnetic material according to any one of claims 1 to 11, wherein the aligned magnetic portion further has an average aspect ratio A / C in the range of 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100, for example 100 to 125, for example 125 to 150, for example 150 to 200, for example 200 to 400, for example 400 to 500.

13. The bulk magnetic material according to any one of claims 1 to 12, wherein the non-aligned magnetic portion further has an average aspect ratio A / C in the range of less than 3.0, for example less than 2.8, for example less than 2.7, for example less than 2.6, for example 2.5 to 1.0, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.

0.

14. The bulk magnetic material according to any one of claims 1 to 13, wherein the average aspect ratio A / C is determined by the crystallite size extracted from X-ray powder diffraction (XRD) analysis or the particle size extracted from transmission electron microscopy (TEM) analysis, preferably determined from the particle size extracted from TEM.

15. The bulk magnetic material according to any one of claims 1 to 14, wherein the material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

16. The bulk magnetic material according to any one of claims 1 to 15, wherein the aligned magnetic portion and the non-aligned magnetic portion are magnetically coupled in a two-phase coupled magnetic system or the like.

17. A method for manufacturing a bulk magnetic material of hexaferrite, wherein the bulk magnetic material includes aligned magnetic portions and non-aligned magnetic portions, and each portion comprises or consists of M-type strontium hexaferrite (SrFe １２ O １９ ), and the method comprises a. A step of providing a first iron-based oxide containing anisotropic crystallites, wherein the anisotropic crystallites are characterized by an average aspect ratio A / C of 5 to 500, the step of providing; b. A step of providing a second iron-based oxide in the form of M-type strontium hexaferrite (SrFe １２ O １９ ), wherein the second iron-based oxide comprises crystallites characterized by an average aspect ratio A / C < 3, said providing step; c. A step of providing a certain amount of alkaline earth metal (aem) precursor; d. A step of mixing the first and second iron-based oxides with the alkaline earth metal (aem) precursor to obtain a final precursor mixture; e. Compressing the final precursor mixture by applying a uniaxial pressure of 200 MPa to 5000 MPa, thereby inducing alignment of the first iron-based precursor to obtain a partially aligned precursor, wherein the second iron-based precursor is not aligned by this step, the obtaining step; f. Heating the partially aligned precursor at a heating rate in the range of 10 °C / hour to 10 °C / second to a temperature in the range of 1000 °C to 1240 °C to convert the partially aligned precursor into the bulk magnetic material of the hexaferrite; g. Isolating the thus-formed bulk magnetic material of the hexaferrite, which comprises aligned magnetic portions and non-aligned magnetic portions, from the reaction mixture, each portion comprising or consisting of M-type strontium hexaferrite (SrFe １２ O １９ ), or consisting thereof, the step of isolating; The method comprising the above. **Claim 18** The method according to claim 17, wherein the hexaferrite does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y). **Claim 19** The first iron-based oxide is goethite, hematite, six-line ferrihydrite, and hexaferrite, for example, M-type hexaferrite, preferably M-type strontium hexaferrite (SrFe １２ O １９ ), or M-type barium hexaferrite (BaFe １２ O １９ ), or M-type calcium hexaferrite (CaFe １２ O １９ ), W-type hexaferrite, and X-type hexaferrite, and the method according to any one of claims 17 to 18, which is selected from the group consisting of **Claim 20** The method according to any one of claims 17 to 19, wherein the first iron-based oxide interacts non-ferromagnetically, such as being non-ferromagnetic under ambient conditions. **Claim 21** The method according to any one of claims 17 to 20, wherein the first iron-based oxide interacts non-ferromagnetically and is selected from goethite, hematite, or 6-line ferrihydrite, preferably goethite. **Claim 22** The method according to any one of claims 17 to 21, wherein the average aspect ratio A / C of the first iron-based oxide is 5 to 10, for example 10 to 15, for example 15 to 20, for example 20 to 30, for example 30 to 40, for example 40 to 50, for example 50 to 75, for example 75 to 100, for example 100 to 125, for example 125 to 150, for example 150 to 200, for example 200 to 400, for example 400 to 500. **Claim 23** The method according to any one of claims 17 to 22, wherein the average aspect ratio A / C of the second iron-based oxide is less than 3.0, for example less than 2.8, for example less than 2.7, for example less than 2.6, for example 2.5 to 1.0, for example 2.5 to 2.0, for example 2.0 to 1.5, for example 1.5 to 1.0, preferably 2.0 to 1.

0. **Claim 24** The method according to any one of claims 17 to 23, wherein the first iron-based oxide and the second iron-based oxide are mixed in a weight ratio ranging from 99:1 to 50:

50.

25. The method according to claim 24, wherein the mixing ratio is in the range of 99:1 to 50:50 by weight, for example, 99:1 to 95:5, for example, 95:5 to 90:10, for example, 90:10 to 85:15, for example, 85:15 to 80:20, for example, 80:20 to 75:25, for example, 75:25 to 70:30, for example, 70:30 to 65:35, for example, 65:35 to 60:40, for example, 60:40 to 55:45, for example, 55:45 to 50:

50.

26. The method according to any one of claims 17 to 25, wherein the alkaline earth metal (aem) precursor is provided in an amount to obtain an Fe / aem molar ratio in the range of 8 to 14, for example, 8 to 9, for example, 9 to 10, for example, 10 to 10.5, for example, 10.5 to 11, for example, 11 to 11.5, for example, 11.5 to 12, for example, 12 to 13, for example, 13 to 14.

27. The method according to any one of claims 17 to 26, wherein the alkaline earth metal (aem) precursor contains an alkaline earth metal selected from the group consisting of Sr, Ba, Ca, Mg, Be, and Ra.

28. The method according to any one of claims 17 to 27, wherein the alkaline earth metal (aem) is selected from the group consisting of Sr and Ba, preferably Sr.

29. The alkaline earth metal (aem) precursor is SrCO ３ , SrO, Sr(OH) ２ , SrCl ２ , Sr(NO ３ ), ２ , SrSO ４ , Sr(OAc) ２ , Sr ３ (PO ４ ), ２ and one or more selected from the group consisting of hydrates thereof, the method according to any one of claims 17 to 28.

30. The alkaline earth metal (aem) precursor is BaCO ３ , BaO, Ba(OH) ２ , BaCl ２ , Ba(NO ３ ), ２ , BaSO ４ , Ba(OAc) ２ , Ba ３ (PO ４ ), ２ and one or more selected from the group consisting of their hydrates, the method according to any one of claims 17 to 29.

31. The method according to any one of claims 17 to 30, wherein the applied uniaxial pressure is 200 MPa to 5000 MPa, for example, 200 MPa to 500 MPa, for example, 500 MPa to 650 MPa, for example, 650 MPa to 800 MPa, for example, 800 MPa to 1000 MPa, for example, 1000 MPa to 1200 MPa, for example, 1200 MPa to 1500 MPa, for example, 1500 MPa to 2000 MPa, for example, 2000 MPa to 3000 MPa, for example, 3000 MPa to 4000 MPa, for example, 4000 MPa to 5000 MPa.

32. The method according to any one of claims 17 to 31, wherein the temperature is 1000°C to 1240°C, for example 1050°C to 1075°C, for example 1075°C to 1100°C, for example 1100°C to 1125°C, for example 1125°C to 1150°C, for example 1150°C to 1175°C, for example 1175°C to 1200°C, for example 1200°C to 1220°C, for example 1220°C to 1240°C.

33. The method according to any one of claims 17 to 32, wherein the heating rate is 10°C / hour to 10°C / minute, for example 10°C / hour to 30°C / hour, for example 30°C / hour to 45°C / hour, for example 45°C / hour to 1°C / minute, for example 1°C / minute to 2°C / minute, for example 2°C / minute to 5°C / minute, for example 5°C / minute to 10°C / minute.

34. A bulk magnetic material obtainable by the method according to any one of claims 17 to 33.

35. The bulk magnetic material includes aligned magnetic portions and non-aligned magnetic portions, a. The aligned magnetic portions are hexagonal platelets of hexaferrite, b. The non-aligned magnetic portions are hexagonal crystallites of hexaferrite, The bulk magnetic material according to claim 34.

36. The bulk magnetic material according to any one of claims 34 to 35, wherein the aligned magnetic portions are uniformly aligned with respect to the bulk magnetic material, the easy magnetization axis of the aligned magnetic portions coincides within ±25° of the surface normal of the bulk magnetic material, and the non-aligned magnetic portions are randomly oriented with respect to the easy magnetization axis and / or the surface normal of the bulk magnetic material.

37. The bulk magnetic material according to any one of claims 34 to 36, further characterized by a coercive force in the range of 200 kA / m to 1000 kA / m.

38. The bulk magnetic material according to any one of claims 35 to 37, wherein the aligned magnetic portions constitute 50% to 99% by weight of the bulk portion of the magnetic material.

39. The bulk magnetic material according to any one of claims 35 to 38, wherein the non-aligned magnetic portions constitute 1% to 50% by weight of the bulk portion of the magnetic material.

40. The aligned and non-aligned magnetic portions of the hexaferrite are M-type strontium hexaferrite (SrFe １２ O １９ ), the bulk magnetic material according to any one of claims 35 to 39.

41. The bulk magnetic material according to any one of claims 35 to 40, wherein the material does not contain rare earth metals such as lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), and yttrium (Y).

42. The method of using the bulk magnetic material according to any one of claims 1 to 16 or 34 to 41 as a magnetic component in a device, or the bulk magnetic material obtained by the method defined in any one of claims 17 to 33.

43. The method of use according to claim 42, wherein the device is an electric motor.

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