183 results about "Magnetocrystalline anisotropy" patented technology

A horizontal magnetic recording medium that has as its magnetic film a granular film with grains of a chemically-ordered FePt or FePtX (or CoPt or CoPtX) alloy in the tetragonal L10 structure uses an etched seed layer beneath the granular film. The granular magnetic film reveals a very high magnetocrystalline anisotropy within the individual grains. The film is produced by sputtering from a single alloy target or cosputtering from several targets. The granular structure and the chemical ordering are controlled by means of sputter parameters, e.g., temperature and deposition rate, and by the use of the etched seed layer that provides a structure for the subsequently sputter-deposited granular magnetic film. The structure of the seed layer is obtained by sputter etching, plasma etching, ion irradiation, or laser irradiation. The magnetic properties, i.e., Hc and areal moment density Mrt, are controlled by the granularity (grain size and grain distribution), the degree of chemical ordering, and the addition of one or more nonmagnetic materials, such as Cr, Ag, Cu, Ta, or B. The resulting granular magnetic film has magnetic properties suitable for application in high-density, horizontal magnetic recording media.

A thermal spring magnetic medium is provided having first and second stacks providing two exchange coupled ferromagnetic layers having different Curie temperatures. The first stack has a high magneto-crystalline anisotropy, a relatively low saturation magnetization and a low Curie temperature. The second stack has a relatively low magneto-crystalline anisotropy, a high saturation magnetization and a high Curie temperature. Preferably the first stack includes an alloy of Fe—Pt or Co—Pt, and the second stack includes an allow of Co—Pt or Co—Pd. A disk drive system having the novel medium is also provided.

A magnetostrictive-piezoelectric multiferroic single- or multi-domain nanomagnet whose magnetization can be rotated through application of an electric field across the piezoelectric layer has a structure that can include either a shape-anisotropic mangnetostrictive nanomagnet with no magnetocrystalline anisotropy or a circular nanomagnet with biaxial magnetocrystalline anisotropy with dimensions of nominal diameter and thickness. This structure can be used to write and store binary bits encoded in the magnetization orientation, thereby functioning as a memory element, or perform both Boolean and non-Boolean computation, or be integrated with existing magnetic tunneling junction (MTJ) technology to perform a read operation by adding a barrier layer for the MTJ having a high coercivity to serve as the hard magnetic layer of the MTJ, and electrical contact layers of a soft material with small Young's modulus. Equivalently, mangnetostrictive nanomagnetic elements whose magnetization is rotated by strain transferred from the substrate that has acoustic waves propagating on the substrate can be used.

A magnetic recording system is provided having a write head employing a combination of magnetic write field gradient and thermal gradient to write data on a ‘thermal spring’ magnetic recording media. The write head comprises a magnetic element using a write current to induce a magnetic write field at the magnetic media and a thermal element using a very small aperture laser to heat a portion of the media. The thermal spring magnetic media comprises [comprises] first and second stacks providing two exchange coupled ferromagnetic layers having different Curie temperatures [The first stack has a high magneto-crystalline anisotropy, a relatively low saturation magnetization and a low Curie temperature.] [The second stack has a relatively low magneto-crystalline anisotropy, a high saturation magnetization and a high Curie temperature.] The magnetic field gradient and the thermal gradient are arranged to substantially overlap at the trailing edge of the heated portion of the magnetic media allowing data at high density with high thermal stability to be recorded on the rapidly cooling thermal spring magnetic recording media.

The invention discloses an ultrahigh-coercivity sintered neodymium-iron-boron magnet and a preparation method thereof. The ultrahigh-coercivity sintered neodymium-iron-boron magnet comprises a main phase and a crystal boundary adding phase. The main phase comprises low-HA main alloy and high-HA main alloy. The high magnetocrystalline anisotropy field HA main alloy and the low-HA main alloy are used as the main phase, so that the heavy rare earth element diffuses from the high-HA phase to the low-HA phase in the sintering and heat treatment process to initially improve the coercivity; in addition, alloy components and the preparation technology can be controlled at the same time, the content of Nd2Fe14B in the magnet is improved, and it is ensured that the magnet has the high magnetic energy product. The crystal boundary adding phase can further achieve crystalline grain surface magnetic hardening and improve the coercivity, the microscopic structure is optimized, and the coercivity is further improved. The preparation method of the ultrahigh-coercivity sintered neodymium-iron-boron magnet has the advantages of both a traditional dual alloy method and a single alloy crystal boundary adding method, and is easy to operate and suitable for mass production of ultrahigh-coercivity high-residual-magnetism sintered neodymium-iron-boron magnets.

Embodiments of the invention provide a thermally assisted magnetic recording medium, which can overcome resistance against thermal fluctuation at RT and write capability, obtain a drastic temperature variation in coercive force at right below the recording temperature, and be formed at low temperature. In one embodiment, the medium has a layered structure formed of a lower high-KF ferromagnetic (F) layer formed on a substrate, satisfying T_W<T_C, an intermediate low-K_AF antiferromagnetic (AF) layer satisfying T_B<T_W, and an upper ferromagnetic (F) layer for recording and reproducing, satisfying T_W<T_C, where T_W is a recording temperature, T_C is a Curie point, T_N is a Neel point, T_B is a blocking temperature, K_F is a ferromagnetic magnetocrystalline anisotropy constant, and K_AF is an antiferromagnetic magnetocrystalline anisotropy constant.

Permanent magnets in which the ferromagnetic phase is matched with the grain boundary phase, and permanent magnets in which magnetocrystalline anisotropy in the vicinity of the outermost shell of the major phase is equivalent in intensity to that in the inside to suppress nucleation of the inverse magnetic domain. Guideline for designing permanent magnets having high magnetic performance is provided.

A magnetic recording medium comprising a substrate, at least one soft magnetic underlayer formed on the substrate, a perpendicular magnetic recording layer formed on the soft magnetic underlayer, and a protective layer formed on the perpendicular magnetic recording layer, is provided wherein the perpendicular magnetic recording layer is comprised of a primary recording layer, a non-magnetic intermediate layer and an auxiliary layer; the primary recording layer comprises magnetic crystal grains and grain boundary portions surrounding the magnetic crystal grains, and has a perpendicular magnetic anisotropy; the auxiliary layer has a negative magneto crystalline anisotropy; and the non-magnetic intermediate layer is formed between the primary recording layer and the auxiliary layer and comprises at least one metal selected from Ru, Rh and Ir, or at least one alloy thereof. This magnetic recording medium exhibits high heat resistance and good recording/reproducing characteristics, and enables a high recording density.

The invention relates to the technical field of rare earth permanent magnetic materials, in particular to a magnetic field orientation three-dimensional printing anisotropic bonded permanent magnet and a preparation method thereof. The magnetic field orientation three-dimensional printing anisotropic bonded permanent magnet, adopts magnet powder having magnetocrystalline anisotropy, comprises one or a plurality of anisotropic neodymium iron boron magnetic powder, samarium cobalt magnetic powder and samarium iron nitrogen powder and is a semi-continuous or continuous orientation changed anisotropic bonded permanent magnet. The magnetic field orientation three-dimensional printing anisotropic bonded permanent magnet is prepared by the following steps of powder filling, orienting and forming into sheet layers, thermal demagnetizing, cutting the sheet layers into required-shaped unit sheet layers, stacking and solidifying the unit sheet layers layer by layer and magnetizing. According to the magnetic field orientation three-dimensional printing anisotropic bonded permanent magnet and the preparation method thereof, preparation of the three-dimensional printing anisotropic bonded permanent magnet is achieved, adjustment of the orientation and the order degree of powder in the sheet layers are achieved by adjusting the magnetic field direction and or the magnetic field strength, the defect that orientation of the traditional bonded permanent magnet cannot be changed is overcame, and continuous or semi-continuous change of magnetic orientation in the same three-dimensional entity is achieved.

This invention relates to magnetic material field and especially to a process method improvement and its formula to hexagonal magnetic lead ferrite powder and sinter magnetism, wherein the said magnetism or magnetic powder has one-Curie temperature with A,R, B and Fe hexagonal ferrite main phase and the following molecular formula: A1-XRx[(Fe3+aFe2+b)12-yBy]zO19, through adding positive three Co and optimizing the formula and improving the magnetism crystal aeolotropism constant K1.

The invention relates to an optimization process method for preparing a high-coercivity permanent magnet by adding heavy rare earth hydroxide into neodymium iron boron. The optimization process method comprises the following steps of: 1, putting heavy rare earth R into a hydrogen environment and heating the heavy rare earth R to 350-450 DEG C to obtain hydroxide of the heavy rare earth R; 2, carrying out ball milling or jet milling in a protective atmosphere of nitrogen or inert gas to obtain micro-powder of the heavy rare earth hydroxide; 3, carrying out hydrogen decrepitation treatment and ball milling or jet milling on an Nd-Fe-B alloy to obtain Nd-Fe-B hydrogen decrepitation micro-power; 4, uniformly mixing two kinds of the micro-power, magnetizing by using a small-frequency alternative and reverse magnetic field pulse, and then isostatically pressing to obtain a press blank; and 5, placing the press blank into a vacuum furnace to sinter and carry out a heat treatment to obtain a high-coercivity sintered magnet. The optimization process method is convenient, simple and reasonable in technology, saves cost and achieves the purpose of improving the coercivity by controlling a microstructure distribution of the magnet, so that the industrial application to preparing the high-temperature high-coercivity rare earth permanent magnet by using trace quantities of heavy rare earth elements with high magneto-crystalline anisotropy becomes possible.

Using specific technique of rapid hardening slice produces alloy based on neodymium (or praseodymium) iron. Then, through reaction of gas-solid phase, crumbling procedure produces RxFe100-x-y-zMyIz magnetic powder. The magnetic powder is single crystal grain in sheet form with average grain size as 1-3 micro. The magnetic powder produced by the disclosed technique possesses anisotropy of magnetocrystalline under action of external magnetic field as well as rolling anisotropy and stress anisotropy. Based on three kinds of anisotropy, the invention discloses method for preparing high performance flexible rubber magnet with rolling anisotropy. The prepared flexible magnet possesses excellent magnetism, flat surface, good cohesiveness, and feasible mechanical properties including tensile strength, extensibility, and rigidity as well as characteristics of temperature resisting, moisture resistance, oil proof and anticorrosion.

Possessing Th2Zn17 type crystal structure, the disclosed material of anisotropic rare earth permanent magnet with its components can be expressed as (Sm1-alphaRalpha)xFe100-x-y-zMyIz, where R as Pr or combination between Pr or other rare earth elements, 0.01<= alpha <=0.30, M selected from Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Nb, Mo, Al, and Zr, I as N only or combination between N and C, 7<=x<=12,0.01<=y<=8.0,6<=z<=14.4. Using the specific technique produces magnetic powder of single crystal grain in sheet form with average grain size as 1-3 micro. The magnetic powder possesses anisotropy of magnetocrystalline under action of external magnetic field as well as rolling anisotropy and stress anisotropy. Based on three kinds of anisotropy, the invention discloses method for preparing high performance flexible rubber magnet with rolling anisotropy.

The invention belongs to the technical field of physical measurement, and in particular relates to a magneto-optic Kerr effect and magnetocrystalline anisotropy field measurement system and a measurement method. The measurement system comprises a magnet control part and a laser detection part. The magnet control part mainly comprises a magnet bracket, power supplies, an ADDA (analog-digital and digital-analog) card and a computer, wherein the computer respectively controls the size and the direction of output current of the two power supplies through the ADDA card, and respectively controls the size and the direction of magnetic fields so as to obtain a required resultant magnetic field; and the laser detection part is composed of a laser device, a polarizer, a polarization analyzer, a photoelectric detector, an ADDA card and a computer, wherein laser emitted by the laser device is projected to the photoelectric detector after being filtered by the polarizer and the polarization analyzer, signals are transmitted to the computer after being converted by the ADDA card, and then Kerr signals of a detection point are obtained. According to the measurement system and the measurement method, the mechanical vibration can be eliminated, the noise in the measurement can be reduced, the accuracy of the measurement can be increased, and magnetic signals and the magnetocrystalline anisotropy field of a sample can be accurately and efficiently obtained.

The invention discloses a novel La-Fe-based magnet with double hard-magnetic main phases and a preparation method for the same, which belong to the technical field of rare-earth permanent magnet materials. The chemical formula of the magnet is expressed to be (LaxRe100-x)aFe100-a-b-cBbTMc, wherein x, a, b and c are used for representing the mass percentages of corresponding elements, moreover, x is not less than 10% and not greater than 60%, a is not less than 29% and not greater than 31%, b is not less than 0.9% and not greater than 1.5%, and c is not less than 0.5% and not greater than 2%; Re is one or several of elements Nd, Pr, Dy, Tb and Ho, and TM is one or several of elements Ga, Co, Cu, Nb and Al. In the magnet disclosed by the invention, La occupies the highest weight in the various rare-earth elements, the content of Nd is less than or equal to 50% of the total of the rare-earth elements, heavy-rare-earth elements are less or not used for general magnets, and an appropriate amount of heavy rare earth needs to be added for preparing high-coercivity magnets. According to the magnet disclosed by the invention, ingredient proportioning is performed by mixing rare earth, thus reducing the cost increased by separation and purification for the rare earth, and rapidly-hardened alloy sheets only needing two ingredients are used for preparing powder by an air-flow mill. According to the magnet and the preparation method disclosed by the invention, a low-temperature sintering technology is used, the sintering temperature is 960-1060 DEG C and tempering is performed at a low temperature; two main phases with different magneto-crystalline anisotropy constants K are contained in the magnet.

A spin transistor conducive to the miniaturization and large scale integration of devices, because a magnetization direction of a source and a drain is determined by a direction of the epitaxial growth of a ferromagnet. The spin transistor includes a semiconductor substrate having a channel layer formed thereinside; ferromagnetic source and drain epitaxially grown on the semiconductor substrate and magnetized in a longitudinal direction of the channel layer due to magnetocrystalline anisotropy—the source and drain being disposed spaced apart from each other in a channel direction and magnetized in the same direction—; and a gate disposed between the source and the drain to be insulated with the semiconductor substrate and formed on the semiconductor substrate to control the spin of electrons that are passed through the channel layer.

The invention discloses a permanent magnet regenerating method of degenerated rare earth permanent magnet material, which comprises the following steps: grinding mechanically; removing impurity; dewetting in the vacuum; proceeding hydrogen disposal or hydrogen disproportionating reaction; adding high-magnetocrystalline anisotropic element and auxiliary texture forming element or alloy; moulding through sintering or adhering to produce anisotropic regenerated permanent magnet. The technology is reasonable with little oxide reaction, which can explore new path for degenerated rare earth permanent magnet.

The invention belongs to the technical field of rare earth permanent magnet materials, and relates to a high-corrosion-resistance multi-hard-magnetic-principal-phase Ce permanent magnet and a preparation method thereof. The permanent magnet is prepared through a process that hydrogen absorption and oxygen control are achieved through powder and dehydrogenation is achieved through pre-sintering. The rare earth element with the maximum mass percentage content in the final magnet is Ce. The chemical formula of the permanent magnet is shown, according to the mass percentage, as (Ce,Re)aFe100-a-b-cBbTMc. The permanent magnet is prepared from multiple hard magnetic principle phases including (Pr,La,Ce,Nd)-Fe-B, (Nd,Pr)-Fe-B and (Dy,Ho,Gd,Er)-Fe-B which are different in particle size and magnetocrystalline anisotropy constant k. The chemical formulas of the principle phase are (RL1-x,Cex)a1Fe100-a1-b1-c1Bb1TMc1, (NdyPr1-y)a2Fe100-a2-b2-c2Bb2TMc2 and [RHz, (Nd,Pr)1-z]a3FE100-a3-b3-c3Bb3TMc3 respectively, wherein x is larger than 0.25 and smaller than or equal to 1.0, y is larger than or equal to 1 and smaller than or equal to 1.0, z is larger than 1 and smaller than or equal to 1.0, a is larger than or equal to 27 and smaller than or equal to 31, b is larger than or equal to 0.8 and smaller than or equal to 1.5, c is larger than or equal to 0.5 and smaller than or equal to 2, the value range of a is the same as those of a1, a2 and a3, the value range of b is the same as those of b1, b2 and b3, and the value range of c is the same as those of c1, c2 and c3. Re is selected from rare earth elements. RL contains light rare earth elements. RH contains heavy rare earth elements. TM is one or more of Ga, Co, Cu, Nb and Al. The permanent magnet has the advantages of being high in corrosion resistance and small in weight-loss ratio, and the preparation technology is suitable for engineering large-scale production.

The invention discloses a preparation method for improving NdFeB (neodymium iron boron) coercivity by organic heavy rare earth complex. The preparation method comprises the following steps: preparing NdFeB alloy particles and smashing the NdFeB particles into powder, and injecting an antioxidant at the same time; injecting mixed liquid of the organic heavy rare earth complex and ethyl ether into the NdFeB alloy powder in a spraying manner; and pressing the mixed material into a blank magnet in a magnetic orientation manner, and sintering the blank magnet. According to the preparation method, the mixture of the rare earth complex and the ethyl ether is added in the spraying manner, so that the contact between the particles and oxygen can be effectively prevented, the oxygen content of the magnetic particles is reduced, and the distribution uniformity of the organic heavy rare earth complex among sintered magnet crystal boundaries is improved; the added organic heavy rare earth complex is degraded along with the rise of the sintering temperature, the residual heavy rare earth ions are uniformly distributed on the surfaces of the NdFeB magnetic particles, and the residual heavy rare earth ions are permeating to the NdFeB particles under a high temperature so as to improve the magnetocrystalline anisotropy and the coercivity of the magnetic main phase; and in addition, the preparation method is simple in process, easy to operate, and suitable for mass production.

A measuring system for measuring the dichroism of the magneto-optical circular polarization with adjustable measuring geometry is provided, whose structure is that: a femtosecond laser excites the white light of the ultra-continuous spectrum, and divides the light by a monochrometer, which forms a monochromatic light whose wavelength can be adjustable. The monochromatic light can polarize through a purified Glan-Taylor prism with the extinction coefficient of 10 <5>; a lantern fly modulator, whose optical axis is 45degree angled with the optical axis of the Glan-Taylor prism to make the light become the circularly polarized light with the alternative variation of the sinistrality and the dextrorotation; a sample, which is put on the center of the cryogenic magnet; The circularly polarized light focuses on the sample, and the reflex reflected from the sample is focuses on the first LED detector; a phase-locking amplifier, whose reference signal is provided by the lantern fly modulator used for testing the difference of light intensity between the sinistrality and the dextrorotation of the circularly polarized light. The invention can not only test the frequency spectrum of the dichroism of the magneto-optical circular polarization of the materials, magnetic density and temperature dependence, but also can test the magnetocrystalline anisotropy of the magnetic semiconductor.

The invention discloses an anisotropic Z-type hexagonal ferrite which is suitable for high and ultrahigh frequency band antennas and has the components: Ba3Me2Fe24O41, wherein Me is one of Co, Zn, Ni, Mg and Cu. The sintering temperature of the anisotropic Z-type hexagonal ferrite is controlled to be from 1150 DEG C to 1300 DEG C; trace oxides are added for regulating a dielectric constant, permeability and the sintering temperature; therefore, a real part epsilon' of the dielectric constant is from 1 to 20; a real part mu' of complex permeability is from 1 to 10; and the dielectric constant or the permeability is basically unchanged as certain values within a certain frequency band of 100 MHz to 3 GHz. The hexagonal ferrite has high cut-off frequency, high dielectric constant and high permeability due to higher magnetic anisotropy field, and can be applied to miniaturization of the sizes of the high and ultrahigh frequency band antennas.

The invention relates to a sintered Nd-Fe-B permanent magnet producing method and belongs to the field of magnetic materials. The sintered Nd-Fe-B permanent magnet preparing method comprises the following steps of smelting, crushing, powder making, pressing for forming, sintering and aging treatment. According to the technical scheme, a certain proportion of abundant rare earth elements including La, Ce and Gd are utilized to partially replace elements Pr, Nd, Dy, Tb and the like, comprehensive utilization of rare earth resources is promoted by means of a produced sintered Nd-Fe-B permanent magnet, and the industrial cost of the sintered Nd-Fe-B permanent magnet is reduced. In the magnet producing process, liquid-phase alloy rich in Pr-Nd phases and liquid-phase alloy rich in La-Ce phases are respectively smelt, the wettability of a main phase and magneto-crystalline anisotropy field of a boundary phase are improved by means of the two rich rare earth phases, and crystal boundary is strengthened by doping Cu-Co nano alloy powder. Compared with a traditional single-alloy method process and a double-alloy method process, intrinsic coercive force and magnetic energy product in the magnet are improved, and the advantages are remarkable.

The invention provides a preparation method for a Zr-Mn-Co multi-doped barium ferrite wave-absorbing material. The preparation method comprises the following steps of: preparing a mixed solution A containing Zr, Mn and Co; adjusting the total molar concentration of the metal ions in the mixed solution A to be 0.01mol/L-0.1mol/L; adding ethylenediamine tetraacetic acid to the mixed solution A to form a solution B; adding a barium source and an iron source to the solution B to form a solution C; adjusting the pH value of the solution C to 8-9 to form uniform and stable transparent sol; preparing the sol into dry sol; carrying out hydrothermal reaction on the dry sol in a water-heating kettle; centrifugally washing the product; and sintering the centrifugally washed materials in a muffle furnace. According to the preparation method provided by the invention, an inorganic salt is used as a precursor, and EDTA (Ethylene Diamine Tetraacetic Acid) is used as a complexing agent to prepare the Zr-Mn-Co multi-doped barium ferrite, so that the crystal morphology and dimension of the barium ferrite are adjusted, thereby providing a novel way for researching the novel water-absorbing agent in stealth materials.