A zero-field-cooled room-temperature exchange-biased permanent magnet material, its preparation method and application

Abstract

The present invention discloses a zero-field-cooled room-temperature exchange bias permanent magnet material, which is composed of two rare earth elements Pr and Gd, and Co element. First, a cast Pr-Gd-Co compound is obtained through melting, and then a Pr-Gd-Co thin strip, that is, the zero-field-cooled room-temperature exchange bias permanent magnet material, is obtained through melt spinning. The atomic ratio satisfies 1:3, and the chemical formula is Pr 1‑ x Gd x Co3, where the value range of x is 0.2 ≤ x ≤ 0.8; the Curie temperature ranges between -400 K and 550 K; the phase structure is a rhombohedral PuNi3-type crystal structure. Its preparation method includes: 1. Preparation of the cast Pr-Gd-Co compound; 2. Preparation of the zero-field-cooled room-temperature exchange bias permanent magnet material. As an application of the permanent magnet material, at room temperature, when the external magnetic field is 2 T, the coercivity is 1.37 - 12.88 kOe; the exchange bias field is 0.2 - 5.38 kOe; at 10 K, when the external magnetic field is 5 T, the coercivity is 16.47 - 36.23 kOe; the exchange bias field is 2.73 - 14.92 kOe. The advantages of the present invention are that it has large coercivity, strong exchange bias field under zero-field-cooled conditions, good temperature stability, and simple process.

Description

Technical Field

[0001] The present invention relates to the field of magnetic functional materials, and particularly to a zero-field-cooled room-temperature exchange-biased permanent magnet material, a preparation method thereof, and an application thereof. Background Art

[0002] In 1956, Meiklejohn and Bean discovered the bias phenomenon of the hysteresis loop in the exchange interaction of the Co-CoO core-shell structure. In the more than 60 years since then, numerous scientists have conducted extensive research on the exchange bias phenomenon and explored its applications in spin valves and magnetic recording media. Initially, the research was focused on the offset phenomenon of the hysteresis loop after applying a magnetic field and cooling. Compared with the hysteresis loop cooled without applying an external magnetic field, the coercivity was improved, which was called the traditional exchange bias. After the cyclic hysteresis loop experiment, the exchange bias field would decrease significantly with the increase of the number of cycles, which was the magnetic training effect. The exchange bias effect generally occurs at the ferromagnetic-antiferromagnetic interface, ferromagnetic-ferromagnetic interface, ferromagnetic-ferrimagnetic interface, and antiferromagnetic-ferrimagnetic interface. The exchange bias effect generated by the interaction between the ferromagnetic and antiferromagnetic interfaces, and the most representative system is the Co-CoO bilayer film.

[0003] For example, in the existing literature 1 (Exchange bias and two steps magnetization reversal in porous Co / CoO layer), J.G. Ovejero et al. prepared Co / CoO nanolayers with different porosities and oxidation degrees in the magnetron sputtering deposition process by adjusting the DC sputtering power, process gas, and target composition. A nanostructured film with a peculiar surface morphology and controllable CoO content was obtained, and the exchange bias field reached up to 2.8 kOe. Although this technical solution obtained a controllable process and achieved good exchange bias performance, there were still four problems: 1. The magnetron sputtering process itself was time-consuming; 2. The cost of the sputtering target was high; 3. The exchange bias would only be generated under the condition of magnetic field cooling, which was greatly limited in practical applications; 4. There was no large exchange bias field at room temperature, and the reported 2.8 kOe exchange bias field could only be achieved at a temperature of 5 K.

[0004] Based on the above problems, in the existing literature 2 (Wang B M, Liu Y, Ren P, et al. Large exchange bias after zero-field cooling from an unmagnetized state[J]. Physical Review Letters, 2011, 106(7):077203.), B.M. Wang et al. melted the NiMn-based Heusler alloy Ni 50 Mn 50-x In x , and prepared an alloy that can exhibit the exchange bias effect under zero-field cooling, solving the complex coating process. Moreover, without external field cooling, a technical effect with a maximum exchange bias field of 1300 Oe was achieved. Although this technical solution can economically and rapidly obtain materials with the exchange bias effect, this zero-field-cooled exchange bias phenomenon is not easy to generate - currently only found in some Heusler alloy systems, perovskite oxide systems, and spinel oxide systems, and most of them also occur at low temperatures, without solving the problem of the working temperature range.

[0005] Regarding the problem of the limitation of the working temperature range, selecting materials with a Curie temperature higher than room temperature is an effective method to increase the working temperature range. While having a high working temperature range, maintaining the characteristic that the exchange bias effect can be generated under zero-field cooling is the technical problem that needs to be solved currently.

[0006] Therefore, in the existing literature 3 (Exchange bias behaviour of amorphous CoFeNiSiB ribbons), L. Zhou et al. used Co 58 Fe5Ni 10 Si 11 B 16 ribbons as raw materials. After longitudinal field annealing with a certain intensity, a zero-field-cooled exchange bias material that can be used at room temperature was obtained. The problems existing in this technical solution are: the material system is complex and requires precise regulation of five elements; moreover, a high coercivity cannot be obtained, with a maximum of only 5 A / m; the exchange bias field is very low, with a maximum of only 0.9 A / m.

[0007] To sum up, the technical difficulties encountered currently can be summarized as:

[0008] 1. The Co-CoO bilayer film system can only exhibit a relatively obvious exchange bias phenomenon when cooled below 100 K in a magnetic field. Almost all materials in the exchange bias system under the condition of field cooling have this drawback. Their performance depends on the external magnetic field and cannot provide a stable exchange bias effect at room temperature, which is not conducive to practical applications.

[0009] 2. The soft magnetic Co 58 Fe5Ni 10 Si 11 B 16 The amorphous ribbon itself is soft magnetic. Only when a microcrystalline hard magnetic phase grows can it interact with the amorphous matrix to produce an exchange bias phenomenon. The coercivity of this material is relatively low, and its application space is limited.

[0010] 3. Among the rapidly quenched hard magnetic thin ribbon samples in other systems, there is no reported zero-field-cooled exchange bias material at room temperature and low temperature that simultaneously has a large coercivity and a large exchange bias phenomenon. Summary of the Invention

[0011] The purpose of the present invention is to provide a zero-field-cooled room-temperature exchange bias permanent magnet material, its preparation method and application.

[0012] The basic principle of the present invention is as follows.

[0013] According to the inventor's previous research, although the exchange bias phenomenon has been found in many material systems, in hard magnetic thin ribbon alloy materials, it is possible to simultaneously have a large coercivity and produce an exchange bias under zero-field-cooled and room-temperature conditions - this technical feature has not been reported in any literature so far.

[0014] In addition, according to the inventor's research, there is a strong exchange bias phenomenon between the double rare earths and the Co element - this technical feature has also not been reported in any literature so far.

[0015] Therefore, by adjusting the ratio of the two rare earth elements Pr and Gd in the present invention and combining them with Co, a new exchange bias material Pr-Gd-Co alloy with zero-field-cooled and room-temperature exchange bias characteristics is obtained. Under the action of the zero-field-cooled exchange bias field, the coercivity at room temperature can be greatly improved. It can be applied to single-polarity pulse transformers, anti-theft systems in libraries and supermarkets, commodity identification, pulse generators, magnetic amplifiers, etc.

[0016] In order to achieve the above-mentioned invention purpose, the technical solution adopted by the present invention is as follows:

[0017] A zero-field-cooled room-temperature exchange-biased permanent magnetic material is composed of two rare earth elements, Pr and Gd, and Co element. First, it is smelted to obtain a as-cast Pr-Gd-Co compound, and then it is processed by melt spinning to obtain a Pr-Gd-Co thin strip, which is the zero-field-cooled room-temperature exchange-biased permanent magnetic material;

[0018] The atomic ratio of the total amount of the two rare earth elements Pr and Gd to the Co element satisfies 1:3; the chemical formula of the Pr-Gd-Co thin strip is Pr 1-x Gd x Co3, where the value range of x is 0.2 ≤ x ≤ 0.8.

[0019] The Curie temperature ranges from 400 K to 550 K; the phase structure of the Pr-Gd-Co thin strip is a rhombohedral PuNi3-type crystal structure.

[0020] A preparation method of a zero-field-cooled room-temperature exchange-biased permanent magnetic material includes the following steps:

[0021] Step 1, preparation of the as-cast Pr-Gd-Co compound. First, weigh the metal elements Pr, Gd, and Co according to a certain Pr-Gd-Co chemical formula. Then, under certain conditions, melt Pr, Gd, and Co to obtain a homogeneous as-cast Pr-Gd-Co compound;

[0022] The Pr-Gd-Co chemical formula in Step 1 meets the following requirements Pr 1-x Gd x Co3, where the value range of x is 0.2 ≤ x ≤ 0.8; the Pr-Gd-Co chemical formula is Pr 0.8 Gd 0.2 Co3, Pr 0.6 Gd 0.4 Co3, Pr 0.5 Gd 0.5 Co3, Pr 0.4 Gd 0.6 Co3, or Pr 0.2 Gd 0.8 Co3, any one of them;

[0023] The melting conditions in Step 1 are as follows: place the metal elements in a copper crucible, under argon atmosphere, with a melting current of 80 - 120 A, and the melting method is to melt back and forth 4 - 6 times;

[0024] Step 2, preparation of the zero-field-cooled room-temperature exchange-biased permanent magnetic material. Subject the as-cast Pr-Gd-Co compound obtained in Step 1 to melt spinning under certain conditions to obtain a Pr-Gd-Co thin strip, which is the zero-field-cooled room-temperature exchange-biased permanent magnetic material;

[0025] The conditions for the spinning treatment in Step 2 are that it is induction melted into a liquid state under the condition of argon with a chamber pressure of 0.04 - 0.06 MPa, and then the spinning treatment is carried out under the condition that the roller speed is 10 - 40 m / s.

[0026] The application of a zero-field-cooled room-temperature exchange-biased permanent magnet material as a permanent magnet material

[0027] At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr-Gd-Co thin strip is 1.37 - 12.88 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 0.2 - 5.38 kOe;

[0028] At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr-Gd-Co thin strip is 16.47 - 36.23 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 2.73 - 14.92 kOe.

[0029] The test results of the zero-field-cooled room-temperature exchange-biased permanent magnet material obtained by the present invention are as follows:

[0030] From the XRD test and EDS test results, it can be seen that the crystal structure of the Pr-Gd-Co thin strip is a single-phase crystal structure of the rhombohedral PuNi3 type; the atomic ratio of the sum of Pr element and Gd element to Co element is 1:3.

[0031] From the metallographic test and TEM test results, it can be seen that a large number of dendrites are distributed on the surface of the Pr-Gd-Co thin strip; the grain size is 14 nm.

[0032] From the hysteresis loop test results, it can be seen that at room temperature, when the external magnetic field is 2 T, the coercivity of the Pr-Gd-Co thin strip is 1.37 - 12.88 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 0.2 - 5.38 kOe; at 10 K, when the external magnetic field is 5 T, the coercivity of the Pr-Gd-Co thin strip is 16.47 - 36.23 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 2.73 - 14.92 kOe.

[0033] Through the above tests, it can be seen that for the first time in the present invention, by the melt spinning technology, Pr 1-x Gd xThe excitation characteristics of the hard magnetic properties and exchange bias effect of Co3 compounds were studied, and the direct relationship between the generation of high coercivity and the rare earth atom ratio and grain size was discovered. Based on this property, by adjusting the ratio of rare earth atoms, the intergranular exchange coupling was adjusted, and finally, through the melt spinning process, smaller grains were obtained to achieve the complex exchange interaction between the amorphous phase and the crystalline phase that generates the exchange bias phenomenon.

[0034] Therefore, compared with the prior art, the present invention has the following advantages:

[0035] 1. By using the method of "argon arc melting + melt spinning", Pr, Gd, and Co metals were metallurgically combined and processed to prepare a ribbon alloy sample that exhibits the exchange bias phenomenon under zero external magnetic field cooling conditions. Excellent properties can be presented without being prepared into a thin film.

[0036] 2. Different from other exchange bias materials that require an external magnetic field to be applied for cooling before the hysteresis loop shifts along the magnetic field axis, this Pr 1-x Gd x Co3 alloy ribbon has a good zero-field-cooled exchange bias effect without applying an external magnetic field, and has good temperature stability and applicability.

[0037] 3. This material has a good zero-field-cooled exchange bias effect at room temperature, which can be arbitrarily adjusted between 10K - 550K, and has good temperature stability and applicability.

[0038] 4. By adjusting the ratio of the two rare earth elements Pr and Gd, through scientific and reasonable design, while the two rare earths coexist and exchange coupling occurs with the Co element to generate the exchange bias phenomenon, a new exchange bias material with zero-field-cooled and room-temperature exchange bias characteristics was developed.

[0039] 5. The Pr 1-x Gd x Co3 alloy ribbon material with zero-field-cooled and room-temperature exchange bias characteristics has a wide range of potential applications, such as giant magnetoresistance, unipolar pulse transformers, magnetic amplifiers, spin valves, etc.

[0040] 6. The as-cast sample of Pr 1-x Gd x Co3 compound is weakly ferromagnetic after melting and heat treatment, but changes to strong ferromagnetism when the melt spinning process is added.

[0041] 7. The Pr 1-x Gd x Co3 as-cast compound shows a large coercivity due to grain refinement after being spun-cast. The coercivity at 10K can reach 36.23 kOe, and the phase purity is high without other impurity phases.

[0042] 8. The preparation method of "argon arc melting + melt spinning" is simple, practical, easy to operate, has few processes, has little dependence on high-precision equipment, and has great industrial application prospects. Description of the Drawings

[0043] Figure 1 for Pr 1-x Gd x Single-phase XRD pattern of Pr

[0044] Figure 2 for Pr 0.4 Gd 0.6 Energy spectrum results of Pr

[0045] Figure 3 for Pr 0.4 Gd 0.6 Morphology diagram of Pr magnified 10,000 times under scanning electron microscope;

[0046] Figure 4 for Pr 0.4 Gd 0.6 Grain size diagram of Pr in the range of 10 nm under transmission electron microscope;

[0047] Figure 5 for Pr 0.4 Gd 0.6 M-H curve of Pr at room temperature and an external magnetic field of 2 T under zero-field cooling;

[0048] Figure 6 for Pr 0.4 Gd 0.6 M-H curve of Pr at 10 K and an external magnetic field of 5 T under zero-field cooling;

[0049] Figure 7 for Pr 1-x Gd x Single-phase XRD pattern of Pr alloy annealed at 800 °C for 7 days;

[0050] Figure 8 for Pr 0.4 Gd 0.6 Morphology diagram of Pr alloy magnified 8,000 times under scanning electron microscope;

[0051] Figure 9 for Pr 0.4 Gd 0.6 M-H curve of Pr alloy annealed at 800 °C for 7 days at room temperature and an external magnetic field of 2 T under zero-field cooling;

[0052] Figure 10 for Pr 0.8Gd 0.2 Morphology diagram of Co3 thin strip magnified 10,000 times under scanning electron microscope;

[0053] Figure 11 is Pr 0.8 Gd 0.2 Energy spectrum result of Co3 thin strip;

[0054] Figure 12 is Pr 0.8 Gd 0.2 M-H curve of Co3 thin strip at room temperature and applied magnetic field of 2 T under zero-field cooling;

[0055] Figure 13 is Pr 0.8 Gd 0.2 M-H curve of Co3 thin strip at 10 K and applied magnetic field of 5 T under zero-field cooling;

[0056] Figure 14 is Pr 0.8 Gd 0.2 Morphology diagram of Co3 alloy magnified 8,000 times under scanning electron microscope;

[0057] Figure 15 is Pr 0.8 Gd 0.2 M-H curve of Co3 alloy annealed at 800 ºC for 7 days at room temperature and applied magnetic field of 2 T under zero-field cooling;

[0058] Figure 16 is Pr 0.6 Gd 0.4 Morphology diagram of Co3 thin strip magnified 10,000 times under scanning electron microscope;

[0059] Figure 17 is Pr 0.6 Gd 0.4 Energy spectrum result of Co3 thin strip;

[0060] Figure 18 is Pr 0.6 Gd 0.4 M-H curve of Co3 thin strip at room temperature and applied magnetic field of 2 T under zero-field cooling;

[0061] Figure 19 is Pr 0.6 Gd 0.4 M-H curve of Co3 thin strip at 10 K and applied magnetic field of 5 T under zero-field cooling;

[0062] Figure 20 is Pr 0.6 Gd 0.4Morphology diagram of Co2 alloy magnified 8000 times under scanning electron microscope;

[0063] Figure 21 is Pr 0.6 Gd 0.4 M-H curve of Co3 alloy annealed at 800 ºC for 7 days under zero-field cooling, at room temperature and an external magnetic field of 2 T;

[0064] Figure 22 is Pr 0.2 Gd 0.8 Morphology diagram of Co3 thin strip magnified 10000 times under scanning electron microscope;

[0065] Figure 23 is Pr 0.2 Gd 0.8 Energy spectrum results of Co3 thin strip;

[0066] Figure 24 is Pr 0.2 Gd 0.8 M-H curve of Co3 thin strip under zero-field cooling, at room temperature and an external magnetic field of 2 T;

[0067] Figure 25 is Pr 0.2 Gd 0.8 M-H curve of Co3 thin strip under zero-field cooling, at 10 K and an external magnetic field of 5 T;

[0068] Figure 26 is Pr 0.2 Gd 0.8 Morphology diagram of Co3 alloy magnified 8000 times under scanning electron microscope;

[0069] Figure 27 is Pr 0.2 Gd 0.8 M-H curve of Co3 alloy annealed at 800 ºC for 7 days under zero-field cooling, at room temperature and an external magnetic field of 2 T.

[0070] Figure 28 is Pr 0.5 Gd 0.5 Morphology diagram of Co3 thin strip magnified 10000 times under scanning electron microscope;

[0071] Figure 29 is Pr 0.5 Gd 0.5 Energy spectrum results of Co3 thin strip;

[0072] Figure 30 is Pr 0.5 Gd 0.5M-H curve of Co3 thin strip under zero-field cooling at room temperature and an external magnetic field of 2 T;

[0073] Figure 31 is Pr 0.5 Gd 0.5 M-H curve of Co3 thin strip under zero-field cooling at 10 K and an external magnetic field of 5 T. Detailed implementation manners

[0074] The present invention will be further described in detail with reference to the accompanying drawings of the specification through embodiments, but it is not a limitation to the present invention. Embodiment

[0075] A preparation method of a zero-field cooled room temperature exchange bias permanent magnet material with the chemical formula Pr 0.4 Gd 0.6 Co3, comprising the following steps:

[0076] Step 1, preparation of as-cast Pr-Gd-Co compound. First, weigh 0.5321 g of metallic element Pr, 0.8816 g of metallic element Gd, and 1.6195 g of metallic element Co according to the chemical formula Pr 0.4 Gd 0.6 Co3. Then, place Pr, Gd, and Co in a copper crucible, and under the condition of argon gas, carry out melting with a melting current of 100 A and a melting method of repeatedly melting forward and backward 4 times to obtain a composition-uniform as-cast Pr-Gd-Co compound;

[0077] Step 2, preparation of zero-field cooled room temperature exchange bias permanent magnet material. Inductively melt the as-cast Pr 0.4 Gd 0.6 Co3 compound obtained in Step 1 into a liquid state under the condition of argon gas with a cavity pressure of 0.05 MPa, and then carry out a spinning process with a roller speed of 25 m / s to obtain Pr 0.4 Gd 0.6 Co3 thin strip, that is, a zero-field cooled room temperature exchange bias permanent magnet material, abbreviated as Pr 0.4 Gd 0.6 Co3 thin strip.

[0078] In order to prove the composition and crystal structure of Pr 0.4 Gd 0.6 Co3 thin strip, XRD test and EDS test are carried out.

[0079] The XRD test results are as Figure 1 shown. The crystal structure of Pr 0.4 Gd 0.6 Co3 thin strip is a single-phase crystal structure of rhombohedral PuNi3 type;

[0080] The EDS test results are as Figure 2 shown, and the atomic ratio of the sum of Pr and Gd elements to Co element is 1:3.

[0081] To prove the surface morphology and grain size of Pr 0.4 Gd 0.6 Co3 ribbon, metallographic test and TEM test are carried out.

[0082] The results of the metallographic test are as Figure 3 shown, and there are a large number of dendrites distributed on the surface of Pr 0.4 Gd 0.6 Co3 ribbon;

[0083] The results of the TEM test are as Figure 4 shown, and the grain size of Pr 0.4 Gd 0.6 Co3 ribbon is 14 nm.

[0084] To prove the zero-field-cooled room-temperature exchange bias performance of Pr 0.4 Gd 0.6 Co3 ribbon, that is, it has the characteristics of a zero-field-cooled room-temperature exchange bias permanent magnet material, a hysteresis loop test is carried out, and the test results are as Figure 5 and Figure 6 shown.

[0085] At room temperature, when the external magnetic field is 2 T, the coercivity of Pr 0.4 Gd 0.6 Co3 ribbon is 9.39 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 2.42 kOe;

[0086] At 10 K, when the external magnetic field is 5 T, the coercivity of Pr 0.4 Gd 0.6 Co3 ribbon is 30.07 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 14.92 kOe;

[0087] The test results show that under zero-field-cooling conditions, Pr 0.4 Gd 0.6 Co3 ribbon has extremely high exchange bias performance at room temperature and 10 K.

[0088] To prove the influence of the preparation process on the hard magnetism and exchange bias effect of the material, Comparative Example 1 is provided, that is, as-cast Pr obtained by conventional heat treatment 0.4 Gd 0.6 Co3.

[0089] Comparative Example 1

[0090] An as-cast Pr0.4 Gd 0.6 The preparation method of Pr-Gd-Co3 is the same as that of Example 1 without description of steps, except that: instead of performing the said step 2, the as-cast Pr-Gd-Co compound obtained in step 1 is subjected to conventional heat treatment under the conditions of an annealing temperature of 800 °C and an annealing time of 7 days, and then the as-cast Pr 0.4 Gd 0.6 Co3 can be obtained.

[0091] In order to prove the composition and crystal structure of the as-cast Pr 0.4 Gd 0.6 Co3, XRD test is carried out. The test results are as Figure 7 shown. The crystal structure of the as-cast Pr 0.4 Gd 0.6 Co3 is a single-phase crystal structure of rhombohedral PuNi3 type, which proves that a single-phase structure with stable structure can also be obtained by conventional heat treatment.

[0092] In order to prove the surface morphology of the Pr 0.4 Gd 0.6 Co3 ribbon, metallographic test is carried out. The test results are as Figure 8 shown. There is only one kind of metallographic structure in the as-cast Pr 0.4 Gd 0.6 Co3.

[0093] In order to prove the zero-field-cooled room-temperature exchange bias performance of the as-cast Pr 0.4 Gd 0.6 Co3, hysteresis loop test is carried out. The test results are as Figure 9 shown. At room temperature, when the external magnetic field is 2 T, the coercivity of the as-cast Pr 0.4 Gd 0.6 Co3 is 0.29 kOe; the hysteresis loop does not shift to the negative axis of the magnetic field H, and there is no exchange bias field.

[0094] It can be proved by Comparative Example 1 that even if the composition and crystal structure are the same, only through the method of the present invention can the zero-field-cooled room-temperature exchange bias performance be obtained.

[0095] In order to prove the above conclusion, Example 2 and Comparative Example 2 are provided, and the zero-field-cooled room-temperature exchange bias permanent magnetic material with the chemical formula of Pr 0.8 Gd 0.2 Co3 and the as-cast Pr 0.8 Gd 0.2 Co3 are compared. Example

[0096] A zero-field-cooled room-temperature exchange bias permanent magnetic material with the chemical formula of Pr 0.8 Gd 0.2Zero-field-cooled room-temperature exchange-biased permanent magnetic material of Pr 0.8 Gd 0.2 Co3, abbreviated as Pr 0.8 Gd 0.2 Co3 ribbon.

[0097] Pr 0.8 Gd 0.2 The SEM test results and EDS results of the Pr Figure 10 and Figure 11 Gd 0.8 Gd 0.2 Co3 ribbon are shown in

[0098] respectively. A large number of dendrites are distributed on the surface of the Pr 0.8 Gd 0.2 Co3 ribbon. The atomic ratio of the sum of Pr element and Gd element to Co element is 1:3. Figure 12 and Figure 13 To prove the zero-field-cooled room-temperature exchange-biased performance of the Pr

[0099] Gd 0.4 Gd 0.6 Co3 ribbon, that is, it has the characteristics of a zero-field-cooled room-temperature exchange-biased permanent magnetic material, a hysteresis loop test is carried out, and the test results are shown in

[0100] respectively. At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr 0.4 Gd 0.6 Co3 ribbon is 1.37 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 0.20 kOe;

[0101] At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr 0.4 Gd 0.6 Co3 ribbon is 22.48 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 2.73 kOe;

[0102] Comparative Example 2

[0103] A preparation method of as-cast Pr 0.8 Gd 0.2 Co3, the steps not described are the same as those in Comparative Example 1, the difference is that: the chemical formula is Pr 0.8 Gd 0.2 Co3, abbreviated as as-cast Pr 0.4 Gd 0.6 Co3.

[0104] To prove the composition and crystal structure of as-cast Pr 0.8 Gd 0.2 Co3, XRD tests were carried out. The test results are as Figure 7 shown. The crystal structure of as-cast Pr 0.8 Gd 0.2 Co3 is a single-phase crystal structure of rhombohedral PuNi3 type, which proves that a single-phase structure with stable structure can also be obtained by conventional heat treatment.

[0105] To prove the surface morphology of Pr 0.8 Gd 0.2 Co3 ribbons, metallographic tests were carried out. The test results are as Figure 14 shown. There is only one kind of metallographic structure in as-cast Pr 0.4 Gd 0.6 Co3.

[0106] To prove the zero-field-cooled room-temperature exchange bias performance of as-cast Pr 0.8 Gd 0.2 Co3, hysteresis loop tests were carried out. The test results are as Figure 15 shown. At room temperature, when the external magnetic field is 2 T, the coercivity of as-cast Pr 0.4 Gd 0.6 Co3 is 0.15 kOe; the hysteresis loop does not shift to the negative axis of the magnetic field H, and there is no exchange bias field.

[0107] Through Example 2 and Comparative Example 2, it can also be proved that even if the composition and crystal structure are the same, only through the method of the present invention can the zero-field-cooled room-temperature exchange bias performance be obtained.

[0108] Based on the above proof idea,

[0109] Example 3 and Comparative Example 3 are provided, a zero-field-cooled room-temperature exchange bias permanent magnet material with the chemical formula Pr 0.6 Gd 0.4 Co3 and as-cast Pr 0.6 Gd 0.4 Co3;

[0110] Example 4 and Comparative Example 4 are provided, a zero-field-cooled room-temperature exchange bias permanent magnet material with the chemical formula Pr 0.2 Gd 0.8 Co3 and as-cast Pr 0.2 Gd 0.8 Co3;

[0111] And Example 5, a zero-field-cooled room-temperature exchange bias permanent magnet material with the chemical formula Pr 0.5 Gd 0.5 Co3. Example

[0112] A zero-field-cooled room-temperature exchange bias permanent magnet material with the chemical formula Pr 0.6 Gd 0.4 Co3. The steps not described are the same as those in Experimental Example 1, except that: the chemical formula in Step 1 is Pr 0.6 Gd 0.4 Co3, abbreviated as Pr 0.6 Gd 0.4 Co3 ribbon.

[0113] Pr 0.6 Gd 0.4 The SEM test results and EDS results of the Pr Figure 16 and Figure 17 Pr 0.6 Gd 0.4 Co3 ribbon are shown as follows. A large number of dendrites are distributed on the surface of the Pr

[0114] To prove the zero-field-cooled room-temperature exchange bias performance of the Pr 0.6 Gd 0.4 Co3 ribbon, that is, to have the characteristics of a zero-field-cooled room-temperature exchange bias permanent magnet material, a hysteresis loop test is carried out, and the test results are as shown in Figure 18 and Figure 19 as follows.

[0115] At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr 0.6 Gd 0.4 Co3 ribbon is 4.50 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 0.46 kOe;

[0116] At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr 0.6 Gd 0.4 Co3 ribbon is 30.63 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 8.06 kOe;

[0117] The test results show that under zero-field cooling conditions, the Pr 0.6 Gd 0.4 Co3 ribbon has extremely high exchange bias performance at both room temperature and 10 K.

[0118] Comparative Example 3

[0119] A preparation method of as-cast Pr 0.6 Gd 0.4 Co3. The steps not described are the same as those in Comparative Example 1, except that: the chemical formula is Pr 0.6 Gd 0.4Co3, referred to as as-cast Pr 0.6 Gd 0.4 Co3.

[0120] In order to prove the composition and crystal structure of as-cast Pr 0.6 Gd 0.4 Co3, XRD tests were carried out. The test results are as Figure 7 shown. The crystal structure of as-cast Pr 0.6 Gd 0.4 Co3 is a single-phase crystal structure of rhombohedral PuNi3 type, which proves that a single-phase structure with stable structure can also be obtained by conventional heat treatment.

[0121] In order to prove the surface morphology of Pr 0.6 Gd 0.4 Co3 ribbons, metallographic tests were carried out. The test results are as Figure 20 shown. There is only one kind of metallographic structure in as-cast Pr 0.6 Gd 0.4 Co3.

[0122] In order to prove the zero-field-cooled room-temperature exchange bias performance of as-cast Pr 0.6 Gd 0.4 Co3, hysteresis loop tests were carried out. The test results are as Figure 21 shown. At room temperature, when the external magnetic field is 2 T, the coercivity of as-cast Pr 0.6 Gd 0.4 Co3 is 0.20 kOe; the hysteresis loop does not shift to the negative axis of the magnetic field H, and there is no exchange bias field. Example

[0123] A zero-field-cooled room-temperature exchange bias permanent magnetic material with the chemical formula Pr 0.2 Gd 0.8 Co3. The steps not described are the same as those in Experimental Example 1. The differences are as follows: The chemical formula in Step 1 is Pr 0.2 Gd 0.8 Co3, referred to as Pr 0.2 Gd 0.8 Co3 ribbons.

[0124] Pr 0.2 Gd 0.8 The SEM test results and EDS results of Pr Figure 22 and Figure 23 are shown as follows. A large number of dendrites are distributed on the surface of Pr 0.2 Gd 0.8 Co3 ribbons. The atomic ratio of the sum of Pr element and Gd element to Co element is 1:3.

[0125] In order to prove Pr 0.2 Gd 0.8The zero-field-cooled room-temperature exchange bias performance of the Pr 0.2 Gd 0.8 Co3 thin strip, that is, it has the characteristics of a zero-field-cooled room-temperature exchange bias permanent magnet material, was subjected to a hysteresis loop test, and the test results are as Figure 24 and Figure 25 shown.

[0126] At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr 0.2 Gd 0.8 Co3 thin strip is 12.88 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 5.38 kOe; Co3 thin strip has a coercivity of 12.88 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 5.38 kOe;

[0127] At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr 0.2 Gd 0.8 Co3 thin strip is 16.47 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 3.96 kOe; Co3 thin strip has a coercivity of 16.47 kOe; the hysteresis loop shifts in the negative direction of the magnetic field H, and the exchange bias field is 3.96 kOe;

[0128] The test results show that under zero-field cooling conditions, the Pr 0.2 Gd 0.8 Co3 thin strip has extremely high exchange bias performance at room temperature and 10 K. Co3 thin strip has extremely high exchange bias performance at both room temperature and 10 K.

[0129] Comparative Example 4

[0130] A preparation method of as-cast Pr 0.2 Gd 0.8 Co3, the steps are not described and are the same as those in Comparative Example 1. The difference is that the chemical formula is Pr 0.2 Gd 0.8 Co3, abbreviated as as-cast Pr 0.2 Gd 0.8 Co3. Co3, abbreviated as as-cast Pr 0.2 Gd 0.8 Co3. Co3.

[0131] In order to prove the composition and crystal structure of as-cast Pr 0.2 Gd 0.8 Co3, XRD testing was carried out. The test results are as Co3, XRD testing was carried out. The test results are as Figure 11 shown. The crystal structure of as-cast Pr 0.2 Gd 0.8 Co3 is a single-phase crystal structure of the PuNi3-type rhombohedral, that is, it is proved that a single-phase structure with stable structure can also be obtained by conventional heat treatment. Co3 is a single-phase crystal structure of the PuNi3-type rhombohedral, that is, it is proved that a single-phase structure with stable structure can also be obtained by conventional heat treatment.

[0132] In order to prove the surface morphology of the Pr 0.2 Gd 0.8 Co3 thin strip, metallographic testing was carried out. The test results are as Co3 thin strip, metallographic testing was carried out. The test results are as Figure 26 shown. There is only one kind of metallographic structure in as-cast Pr 0.2 Gd 0.8 Co3. Co3 only exists in one kind of metallographic structure.

[0133] In order to prove as-cast Pr​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​0.2 Gd 0.8 The zero-field-cooled room-temperature exchange bias performance of Co3 was tested by a hysteresis loop test. The test results are as Figure 27 shown. At room temperature, when the external magnetic field is 2 T, the coercivity of as-cast Pr 0.2 Gd 0.8 Co3 is 0.30 kOe; the hysteresis loop does not shift to the negative axis of the magnetic field H, and there is no exchange bias field. Example

[0134] A zero-field-cooled room-temperature exchange bias permanent magnetic material with the chemical formula Pr 0.5 Gd 0.5 Co3. The steps not described are the same as those in Experimental Example 1, except that: the chemical formula in Step 1 is Pr 0.5 Gd 0.5 Co3, abbreviated as Pr 0.5 Gd 0.5 Co3 thin strip.

[0135] Pr 0.5 Gd 0.5 The SEM test results and EDS results of the Pr Figure 28 and Figure 29 are shown as follows. A large number of dendrites are distributed on the surface of the Pr 0.5 Gd 0.5 Co3 thin strip, and the atomic ratio of the sum of Pr and Gd elements to Co element is 1:3.

[0136] To prove the zero-field-cooled room-temperature exchange bias performance of the Pr 0.5 Gd 0.5 Co3 thin strip, that is, it has the characteristics of a zero-field-cooled room-temperature exchange bias permanent magnetic material, a hysteresis loop test was carried out, and the test results are as Figure 30 and Figure 31 shown.

[0137] At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr 0.5 Gd 0.5 Co3 thin strip is 6.54 kOe; the hysteresis loop shifts to the negative direction of the magnetic field H, and the exchange bias field is 0.92 kOe;

[0138] At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr 0.5 Gd 0.5 Co3 thin strip is 36.23 kOe; the hysteresis loop shifts to the negative direction of the magnetic field H, and the exchange bias field is 13.06 kOe;

[0139] The test results show that under zero-field cooling conditions, Pr 0.5 Gd 0.5The Co3 thin strip exhibits extremely high exchange bias performance at both room temperature and 10 K.

[0140] The above-mentioned examples and comparative examples directly prove that the method of the present invention can obtain zero-field-cooled room-temperature exchange bias performance.

[0141] In addition, for the material of the present invention at a temperature of 10 K, the maximum coercive force is 36.23 kOe; while the maximum coercive force of the material obtained by the conventional method is only 0.3 kOe.

Claims

1. A preparation method of a zero-field-cooled room-temperature exchange-biased permanent magnet material, characterized in that It includes the following steps: Step 1: Preparation of as-cast Pr-Gd-Co compound. First, weigh the metal elements Pr, Gd, and Co according to a certain Pr-Gd-Co chemical formula. Then, under certain conditions, melt Pr, Gd, and Co to obtain a compositionally uniform as-cast Pr-Gd-Co compound; The Pr-Gd-Co chemical formula in step 1 meets the following requirements Pr 1-x Gd x Co3, where the value range of x is 0.2 ≤ x ≤ 0.8; The melting conditions in Step 1 are as follows: place the metal elements in a copper crucible, and under an argon atmosphere, melt them with a melting current of 80 - 120 A and a melting method of repeatedly melting forward and backward 4 - 6 times; Step 2: Preparation of zero-field-cooled room-temperature exchange-biased permanent magnetic material. Subject the as-cast Pr-Gd-Co compound obtained in Step 1 to a melt spinning process under certain conditions to obtain a Pr-Gd-Co thin strip, which is the zero-field-cooled room-temperature exchange-biased permanent magnetic material; The conditions for the melt spinning process in Step 2 are as follows: under an argon atmosphere with a chamber pressure of 0.04 - 0.06 MPa, melt it into a liquid state by induction melting, and then perform the melt spinning process at a roll speed of 10 - 40 m / s.

2. The preparation method according to claim 1, wherein: The chemical formula of Pr-Gd-Co in step 1 is Pr 0.8 Gd 0.2 Co3, Pr 0.6 Gd 0.4 Co3, Pr 0.5 Gd 0.5 Co3, Pr 0.4 Gd 0.6 Co3 or Pr 0.2 Gd 0.8 Any one of Co3.

3. The zero-field-cooled room-temperature exchange-biased permanent magnetic material obtained by the preparation method according to claim 1, characterized in that: The Curie temperature ranges from 400 K to 550 K; the phase structure of the Pr-Gd-Co thin strip is a rhombohedral PuNi3-type crystal structure.

4. Use of the zero-field-cooled room-temperature exchange-biased permanent magnet material obtained by the preparation method according to claim 1 as a permanent magnet material, characterized in that: At room temperature, when the external magnetic field is 2 T, the coercivity of the Pr-Gd-Co thin strip is 1.37 - 12.88 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 0.2 - 5.38 kOe.

5. Use of the zero-field-cooled room-temperature exchange-biased permanent magnet material obtained by the preparation method according to claim 1 as a permanent magnet material, characterized in that: At 10 K, when the external magnetic field is 5 T, the coercivity of the Pr-Gd-Co thin strip is 16.47 - 36.23 kOe; the hysteresis loop shifts towards the negative direction of the magnetic field H, and the exchange bias field is 2.73 - 14.92 kOe.

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