Double-perovskite oxide ceramic with exchange bias effect and preparation method thereof
By using Sr2+-doped Nd2-xSrxCoMnO6 double perovskite oxide ceramics, the problems of complex preparation of exchange bias effect materials and magnetic training effect have been solved, realizing stable exchange bias and low-energy magnetic storage and sensing applications.
Patent Information
- Application Number
- CN202512039377.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-20
AI Technical Summary
Existing exchange bias effect materials have complex preparation processes, many material defects and unstable properties, and the magnetic training effect, which causes the exchange bias to gradually decrease with repeated magnetization, affects the performance of magnetoresistive devices.
The Nd2-xSrxCoMnO6 (0.0≤x≤0.5) double perovskite oxide ceramic was prepared by Sr2+ doping to control the crystal structure and spin structure. The preparation method included multi-stage sintering to avoid high-temperature gas release and ensure the material's density.
It achieves stability of the exchange bias effect, reduces magnetic annealing effect, has fewer material defects, and low energy consumption, making it suitable for electronic components such as high-density magnetic storage devices and sensors.
Smart Images
Figure CN121698652A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of magnetic recording media and magnetic multifunctional materials, specifically to a double perovskite oxide ceramic with exchange bias effect and its preparation method. Background Technology
[0002] In an external magnetic field, a ferromagnetic / antiferromagnetic system moves from a temperature above the antiferromagnetic Nell temperature. T N And below the Curie temperature of the ferromagnetic layer T C ( T N < T < T C When cooled below the antiferromagnetic Nell temperature (i.e., after field cooling), the hysteresis loop of the ferromagnetic layer deviates from the origin along the magnetic field direction (the amount of deviation is called the exchange bias field), accompanied by an increase in coercivity. This phenomenon is called exchange bias. Meikleijohn and Bean first discovered this effect in Co / CoO ferromagnetic / antiferromagnetic core-shell structured particles in 1956. Subsequently, the exchange bias phenomenon was observed in materials containing ferromagnetic / antiferromagnetic interfaces, such as nanoparticles, bilayer films, and some alloys and compounds without clear magnetic interaction interfaces. With the discovery of the spin valve effect based on the exchange bias effect, it has become an important foundation of modern information storage technology, widely applied in permanent magnets, spin valves, high-density magnetic storage, and sensing. Therefore, the exchange bias effect has received widespread attention and research due to its significant importance in both basic research and applications.
[0003] Exchange bias effects are commonly found in heterostructures, but the fabrication processes for heterostructured materials are complex, resulting in numerous material defects and unstable properties. Therefore, recent research has focused on developing and designing single-phase ceramic materials with exchange bias effects, such as perovskite-like rare-earth manganese oxides (Pr) where ferromagnetic and antiferromagnetic phases coexist. 1 / 3Ca 2 / 3 An exchange bias effect was observed in MnO3. This class of materials also includes La. 0.25 Ca 0.75 MnO3, Y 0.2 Ca 0.8MnO3, etc., but overall the types are rare. Double perovskite oxides are named in contrast to perovskite ABO3 type oxides, with the general formula A2B′B"O6, where A is generally a rare earth element or alkaline earth element, and B′ and B" are generally transition metal elements. Among the many A2B′B"O6 systems, such as the monoclinic Y2CoMnO6 with space group P21 / n (Harikrishnan S. Nair, TapanChatterji, and Andre M. Strydom, Antisite disorder-induced exchange biaseffect in multiferroic Y2CoMnO6, Applied Physics Letters, 2015, 106: 022407.) and Sr-doped Y... 2-x Sr x CoMnO6( x =0, 0.25, 0.5) (Chunlin Ma, Xingyu Wang, Mengxiong Cao, et al., Magnetic properties and exchange bias effect of Y 2-x Sr x CoMnO6(0≤ x ≤0.5) double perovskites, Journal of Materials Science: Materials in Electronics, 2018, 29: 17818-17825.) and La with a mixed structure of monoclinic and rhombohedral. 2- x Sr x CoMnO6( x =0.05, 0.1, 0.15, 0.2, 0.3, 0.5) (Lei Xing, Qiuhang Li, Mingxiang Xu, Exchange bias and magnetoresistance effects in La 2-x Sr x CoMnO6 (0.05≤ x Exchange bias effects were found in systems such as (≤0.5), Journal of Alloys and Compounds, 2019, 774: 646-650.), and the Co-induced by antisite disorder was also observed. 2+ -O 2- -Co 2+Co 3+ -O 2- -Co 3+ It is related to antiferromagnetic effects.
[0004] Furthermore, in exchange-biased systems, the exchange bias typically decreases gradually with continuous and repeated magnetization; this degradation phenomenon is known as the "training effect." The exchange bias observed in both the Y₂CoMnO₆ and Sr-doped La₂CoMnO₆ systems exhibits a significant magnetic training effect. The presence of this magnetic training effect severely impacts the performance of magnetoresistive devices; therefore, reducing or eliminating the magnetic training effect in practical devices is of great importance. Summary of the Invention
[0005] To address the aforementioned problems, this invention provides a double perovskite oxide ceramic with an exchange bias effect and its preparation method. The double perovskite ceramic material is Nd... 2-x Sr x CoMnO6 (0.0≤ x ≤0.5), has a single-phase orthogonal structure, and has a high Curie temperature. T C Nell temperature T N Approximately or above liquid nitrogen temperature (77 K). The undoped Nd₂CoMnO₆ system exhibits an exchange bias effect, and this exchange bias lacks a magnetic training effect. Sr 2+ Doped Nd 2-x Sr x CoMnO6 (0.0< x ≤0.5) alters the crystal structure and spin structure of the system, thereby effectively controlling the magnetic order type, phase transition temperature and exchange bias field of the material. Moreover, the magnetic training effect of the exchange bias is weak and can be almost ignored.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: The purpose of this invention is to provide a double perovskite oxide ceramic with an exchange bias effect, wherein the chemical formula of the double perovskite oxide ceramic is Nd. 2-x Sr x CoMnO6, of which Sr 2+ For doped ions, molar doping amount x 0.0≤ x ≤0.5; the double perovskite oxide ceramic has a single-phase orthogonal structure; when x When σ = 0.0, the chemical formula of the double perovskite oxide ceramic is Nd₂CoMnO₆. The double perovskite oxide ceramic exhibits an exchange bias effect, and this exchange bias does not possess a magnetic tempering effect; when 0.0 < σ, the chemical formula is Nd₂CoMnO₆. x When Sr ≤ 0.5 2+The crystal structure and spin structure of the doping-induced system change, thereby controlling the magnetic order type, phase transition temperature and exchange bias field.
[0007] In a preferred embodiment of the present invention, when Sr 2+ molar doping amount x The Curie temperature of Nd2CoMnO6 when it is 0.0 T C1 For 160K, T C2 At 140K, under a magnetic field of 70kOe, the maximum magnetic moment is 58 emu / g, and under a cooling magnetic field of 1kOe, the exchange bias field is 2.8kOe; when Sr 2+ molar doping amount x =0.0< x When ≤0.5, in T C1 The paramagnetic-ferromagnetic phase transition that occurs gradually disappears with increasing doping concentration, and the Curie temperature... T C2 The range is 128K~141K. Under a magnetic field of 70kOe, the maximum magnetic moment is 35emu / g~55emu / g. Under a cooling magnetic field of 1kOe, the exchange bias field is 2.1kOe~3.6kOe.
[0008] Another object of the present invention is to provide a method for preparing the above-mentioned double perovskite oxide ceramic with exchange bias effect, comprising the following steps: S1. Weigh neodymium oxide, cobalt oxide, manganese dioxide and strontium carbonate according to the stoichiometric ratio to obtain a mixture.
[0009] S2. Using the mixture as raw material, grind it and then pre-calcine it in air to obtain the first pre-calcine product.
[0010] S3. Using the first pre-calcined product as raw material, grind it and then pre-calcine it in air to obtain the second pre-calcined product.
[0011] S4. Using the second pre-calcination product as raw material, the product is ground, compressed into tablets, and then calcined in air to form a single-phase orthogonal structure, yielding Nd. 2-x Sr x CoMnO6 is a double perovskite oxide ceramic with exchange bias effect.
[0012] In a preferred embodiment of the present invention, the temperature of the first pre-firing is 900℃~1050℃, and the time is 10h~12h.
[0013] In a preferred embodiment of the present invention, the temperature of the second pre-firing is 1100℃~1250℃, and the time is 10h~12h.
[0014] In a preferred embodiment of the present invention, the calcination temperature is 1350℃~1400℃ and the time is 20h~24h.
[0015] In a preferred embodiment of the present invention, the heating rates for the first pre-firing, the second pre-firing, and the calcination are all 3°C / min to 5°C / min.
[0016] In a preferred embodiment of the present invention, the pressure of the tablet is 10MPa to 16MPa.
[0017] In a preferred embodiment of the present invention, after the first pre-firing, the second pre-firing, and the calcination are completed, the cooling method is to cool the furnace to room temperature.
[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a double perovskite Nd2 with exchange bias effect. 2-x Sr x CoMnO6 (0.0≤ x ≤0.5) ceramic material, with a single-phase orthogonal structure and a high Curie temperature. T C Nell temperature T N The temperature is close to or higher than that of liquid nitrogen (77K). The Nd₂CoMnO₆ prepared in this invention exhibits a significant exchange bias effect without ion doping, and this exchange bias system does not exhibit magnetic training effect, which is of great significance in practical applications. By changing Sr... 2+ The doping level induces lattice distortion, generates Co / Mn antisite disorder, and alters the oxygen vacancy defect content, leading to Co... 2+ -O 2- -Mn 4+ Co 3+ -O 2- -Mn 3+ Ferromagnetic exchange interaction and Co 2+ -O 2- -Co 2+ Mn 4+ -O 2- -Mn 4+ Co 3+ -O 2- -Co 3+ The antiferromagnetic exchange interactions compete and coexist, thereby effectively controlling the magnetic order type, phase transition temperature, and exchange bias field of the material. Among these, the cooling magnetic field... H cooled =1kOe, measuring magnetic field H max When the bias field is 70kOe, the exchange bias field is used. H EBThe value is 2.1 kOe to 3.6 kOe. Therefore, the bias field is exchanged. H EB The exchange bias field can be altered by changing the Sr doping amount or adjusted according to the application. Furthermore, after continuous cyclic measurements, the exchange bias field decreased by 3.2% between the first and second cycles, and by the tenth cycle, the exchange bias field decreased by 4.5%, indicating that the exchange bias effect has a weak magnetic training effect and can be almost ignored.
[0019] 2. This invention provides a method for preparing double perovskite oxide ceramics with exchange bias effect. Compared with existing technologies such as magnetron sputtering, molecular beam epitaxy, and pulsed laser deposition commonly used in multilayer films and heterojunction materials, this method has the advantages of simple and easy-to-operate equipment, easy control of sample component ratios, low raw material prices, low cost, no need to add solvents, green and environmentally friendly, and pollution-free. In addition, no reaction atmosphere is required during the reaction process, the product is easy to collect, and it can be prepared in large quantities.
[0020] 3. The double perovskite oxide ceramic with exchange bias effect provided by this invention, compared with multilayer films, heterojunctions and other materials, has fewer defects, smaller elastic strain and smaller stress coupling of single-phase compound materials. Therefore, it has lower energy consumption and is more environmentally friendly when applied. It has broad development prospects and application value in the field of electronic components such as high-density magnetic storage devices and sensors. Attached Figure Description
[0021] Figure 1 The images show the XRD patterns of the ceramic samples from Examples 1 to 6 of this invention.
[0022] Figure 2 The O1s XPS spectra and peak division results of the ceramic samples of Examples 1 to 6 of this invention are shown. Figure 2 (a) shows the O1s XPS spectrum and peak division results of Example 1, (b) shows the O1s XPS spectrum and peak division results of Example 2, (c) shows the O1s XPS spectrum and peak division results of Example 3, (d) shows the O1s XPS spectrum and peak division results of Example 4, (e) shows the O1s XPS spectrum and peak division results of Example 5, and (f) shows the O1s XPS spectrum and peak division results of Example 6.
[0023] Figure 3 The images show the Raman spectra of the ceramic samples from Examples 1 to 6 of this invention.
[0024] Figure 4 The graphs show the magnetization intensity of ceramic samples from Examples 1 and 2 of this invention under zero-field cooling and field-cooled conditions when the applied magnetic field is 1 kOe, as a function of temperature. Figure 4Figure (a) shows the magnetization intensity as a function of temperature in Example 1, and Figure (b) shows the magnetization intensity as a function of temperature in Example 2.
[0025] Figure 5 The graphs show the magnetization intensity of ceramic samples from Examples 3 to 6 of this invention under zero-field cooling and field-cooled conditions when the applied magnetic field is 1 kOe, as a function of temperature. Figure 5 Figure (a) shows the magnetization intensity as a function of temperature in Example 3; Figure (b) shows the magnetization intensity as a function of temperature in Example 4; Figure (c) shows the magnetization intensity as a function of temperature in Example 5; and Figure (d) shows the magnetization intensity as a function of temperature in Example 6.
[0026] Figure 6 The graphs show the magnetization intensity of ceramic samples from Examples 1 to 6 of this invention under zero-field cooling and field-cooled conditions at 2K as a function of magnetic field. Figure 6 Figure (a) shows the magnetization intensity as a function of magnetic field in Example 1; Figure (b) shows the magnetization intensity as a function of magnetic field in Example 2; Figure (c) shows the magnetization intensity as a function of magnetic field in Example 3; Figure (d) shows the magnetization intensity as a function of magnetic field in Example 4; Figure (e) shows the magnetization intensity as a function of magnetic field in Example 5; and Figure (f) shows the magnetization intensity as a function of magnetic field in Example 6.
[0027] Figure 7 The graphs show the changes in exchange bias field and coercivity of ceramic samples from Examples 1 to 6 of this invention as a function of doping amount at a temperature of 2K and a cooling magnetic field of 1kOe.
[0028] Figure 8 The images show 10 hysteresis loop diagrams of the ceramic samples from Examples 1 and 4 of this invention, continuously cyclically measured at a temperature of 2K under a cooling magnetic field of 5kOe. Figure 8 Figure (a) is the hysteresis loop diagram of Example 1, and Figure (b) is the hysteresis loop diagram of Example 4.
[0029] Figure 9 The exchange bias field is obtained by continuously cyclically measuring the hysteresis loop 10 times under a cooling magnetic field of 5 kOe at a temperature of 2 K for the ceramic samples of Examples 1 and 4 of this invention. H EB A graph showing the relationship between the number of measurements (n) and the measurement frequency (n). Detailed Implementation
[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0031] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.
[0032] Exchange bias effects are commonly found in heterostructures, but the fabrication processes for heterostructure materials are complex, resulting in numerous material defects and unstable properties. Therefore, recent research has focused on developing and designing single-phase ceramic materials with exchange bias effects, such as perovskite-like rare-earth manganese oxides (Pr) where ferromagnetic and antiferromagnetic phases coexist. 1 / 3 Ca 2 / An exchange bias effect was observed in 3MnO3. This class of materials also includes La. 0.25 Ca 0.75 MnO3, Y 0.2 Ca 0.8 MnO3, etc., are examples, but their variety is generally limited. The general formula for double perovskite oxides is A2B′B"O6, where A is typically a rare earth element or alkaline earth element, and B′ and B" are typically transition metal elements. Furthermore, in exchange-biased systems, the exchange bias typically decreases gradually with continuous and repeated magnetization; this degradation phenomenon is called the "training effect." Significant magnetic training effects are observed in the exchange bias of Y2CoMnO6 and Sr-doped La2CoMnO6 systems. The presence of the magnetic training effect severely affects the performance of magnetoresistive devices; therefore, reducing or eliminating the magnetic training effect in practical devices is of great significance.
[0033] Based on this, on the one hand, the present invention provides a double perovskite oxide ceramic with an exchange bias effect, wherein the chemical formula of the double perovskite oxide ceramic is Nd 2-x Sr x CoMnO6, of which Sr 2+ For doped ions, molar doping amount x 0.0≤ x ≤0.5; the double perovskite oxide ceramic has a single-phase orthogonal structure. For undoped Nd2CoMnO6 ( x=0.0), the formation of oxygen vacancy defects leads to changes in the spin structure of the system. The ferromagnetic and antiferromagnetic exchange interactions between Co and Mn ions compete and coexist, causing an exchange bias effect, and this exchange bias does not have a magnetic forging effect. Sr 2+ Doping induces changes in the crystal structure and spin structure of the system by causing lattice distortion, generating Co / Mn antisite disorder, and changing the oxygen vacancy defect content. It has an effective control effect on the magnetic order type, phase transition temperature and exchange bias field of the material. Moreover, the exchange bias has a weak magnetic training effect, which can be almost ignored.
[0034] It should be noted that in the double perovskite oxide ceramic structure, Sr 2+ As a dopant, molar doping amount x 0.0≤ x ≤0.5; The double perovskite oxide ceramic has a single-phase orthogonal structure. Undoped Nd₂CoMnO₆ forms oxygen vacancy defects during high-temperature sintering and rapid cooling, leading to Co... 2+ and Mn 4+ The ion valence state changes, and Co appears. 3+ and Mn 3+ This allows for the manipulation of the spin structure, resulting in an exchange bias effect in the system. Under a 1 kOe cooling magnetic field, the exchange bias field... H EB The value is 2.8 kOe, and this exchange bias does not exhibit a magnetic forging effect. Sr 2+ Doping induces crystal structure distortion, generates Co / Mn antisite disorder, and alters the oxygen vacancy defect content. The ferromagnetic and antiferromagnetic exchange interactions between Co and Mn ions compete and coexist, significantly regulating the exchange bias effect.
[0035] The aforementioned when Sr 2+ molar doping amount x When the value is 0.0, the Curie temperature of Nd2CoMnO6 is... T C1 ~160K, T C2 At ~140K, under a magnetic field of 70kOe, the maximum magnetic moment is 58 emu / g; under a cooling magnetic field of 1kOe, the exchange bias field is 2.8kOe; when Sr 2+ molar doping amount x =0.0< x When ≤0.5, in T C1 The paramagnetic-ferromagnetic phase transition that occurs gradually disappears with increasing doping concentration, and the Curie temperature... T C ( T C2The magnetic field strength ranges from 128K to 141K. Under a magnetic field of 70kOe, the maximum magnetic moment is 35emu / g to 55emu / g. Under a cooling magnetic field of 1kOe, the exchange bias field is 2.1kOe to 3.6kOe.
[0036] It should be noted that the Nd2 double perovskite oxide ceramic 2-x Sr x CoMnO6 has a single-phase orthogonal structure, with Sr 2+ With increasing doping concentration, the CoO6 octahedron and MnO6 octahedron undergo structural distortion, resulting in antisite disorder in the system. The oxygen vacancy defect content changes, and the changes in crystal structure and spin structure induce changes in the magnetic exchange interaction of the system, thereby weakening the ferromagnetism and enhancing the antiferromagnetism, thus regulating the exchange bias effect.
[0037] On the other hand, the present invention provides a method for preparing the above-mentioned double perovskite oxide ceramic with exchange bias effect, characterized by comprising the following steps: S1. Weigh neodymium oxide (Nd2O3), cobalt oxide (Co3O4), manganese dioxide (MnO2), and strontium carbonate (SrCO3) according to the stoichiometric ratio to obtain a mixture.
[0038] S2. Using the mixture as raw material, the mixture is first ground and then pre-calcined in air. The metal oxides undergo initial decomposition and recombination, which enhances ionic activity to facilitate subsequent reactions and forms simple composite oxides or solid solutions. Strontium carbonate is decomposed to remove organic matter. The moisture and trace impurity gases adsorbed on the raw material are removed, and the mixture is cooled to room temperature to obtain the first pre-calcined product.
[0039] S3. Using the first pre-calcined product as raw material, perform a second grinding, and then perform a second pre-calcination in air. The intermediate is transformed, and a double perovskite phase is initially generated. Cool to room temperature to obtain the second pre-calcined product.
[0040] S4. Using the second pre-calcined product as raw material, after the third grinding and pressing, it is calcined in an air atmosphere. A small amount of incompletely reacted intermediates further react to eliminate residual impurities and promote lattice ordering, thereby forming a single-phase dense structure. After cooling to room temperature, double perovskite oxide ceramics are obtained.
[0041] The temperature of the first pre-firing is 900℃~1050℃, and the time is 10h~12h.
[0042] The second pre-firing temperature is 1100℃~1250℃, and the time is 10h~12h.
[0043] The calcination temperature is 1350℃~1400℃, and the time is 20h~24h.
[0044] This invention employs a staged sintering method to gradually remove impurities and carbonate decomposition products, avoiding the violent release of gas caused by a single high-temperature sintering process, which could lead to cracking or excessive porosity in the green body. Controlling the reaction rate allows for initial diffusion and low-temperature reactions between raw materials, forming an intermediate phase that lays a uniform foundation for subsequent high-temperature sintering and reduces component segregation. Relieving thermal stress through stepwise heating also results in a gentler internal temperature gradient, preventing cracks caused by differences in thermal expansion and contraction and ensuring the structural integrity of the green body.
[0045] The heating rates for the first pre-firing, the second pre-firing, and the calcination are all 3℃ / min to 5℃ / min.
[0046] The first grinding time is 6-8 hours, the second grinding time is 4-6 hours, and the third grinding time is 2-4 hours. Multiple grinding processes improve the uniformity of raw material mixing and reactivity, laying the foundation for subsequent sintering and material properties. Reducing particle size increases the specific surface area of the raw materials, allowing for more sufficient contact between particles and lowering the activation energy of subsequent reactions. Breaking up particle agglomerates avoids localized component segregation, ensuring a uniform distribution of all components at the microscale.
[0047] The pressure of the tablet is 10MPa~16MPa, and the diameter of the resulting disc is 10mm and the thickness is 1.5mm.
[0048] After the first pre-firing, the second pre-firing, and the calcination are completed, the furnace must be cooled to room temperature.
[0049] The following specific examples will provide further explanation.
[0050] Example 1 A method for preparing a double perovskite oxide ceramic Nd2CoMnO6 includes the following steps: S1. According to the stoichiometric ratio of Nd2CoMnO6, weigh Nd2O3, Co3O4 and MnO2 with a purity greater than 99.9%, and then grind them in an agate mortar for 6 hours to obtain a uniformly mixed powder.
[0051] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 900°C at a heating rate of 3°C / min in an air atmosphere and hold for 10 hours for pre-firing. After pre-firing, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0052] S3. Place the cooled powder in an agate mortar and grind it for a second time for 4 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat it to 1100°C at a heating rate of 3°C / min in an air atmosphere and hold it for 10 hours for a second pre-firing. After the pre-firing is completed, cool it to room temperature with the furnace to obtain the powder after the second cooling.
[0053] S4. After the powder has been cooled twice, it is ground three times for 2 hours to make it uniformly mixed. Then, a pressure of 10 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0054] S5. The disc was heated to 1350℃ in air at a heating rate of 3℃ / min and held at that temperature for 20h. Finally, it was cooled to room temperature in the furnace to obtain a double perovskite oxide ceramic, namely Nd2CoMnO6 ceramic sample.
[0055] Example 2 A strontium-doped double perovskite oxide ceramic Nd 1.9 Sr 0.1 The preparation method of CoMnO6 includes the following steps: S1, according to Nd 1.9 Sr 0.1 The stoichiometric ratio of CoMnO6 elements was determined by weighing Nd2O3, Co3O4, MnO2 and SrCO3 with a purity greater than 99.9%, and then grinding them in an agate mortar for 7 hours to obtain a uniformly mixed powder.
[0056] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 950°C at a heating rate of 3°C / min in an air atmosphere and hold for 10 hours for pre-firing. After pre-firing, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0057] S3. Place the cooled powder in an agate mortar and grind it for 5 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat the powder to 1150°C at a heating rate of 3°C / min in an air atmosphere and hold it for 10 hours for a second pre-firing. After the pre-firing is completed, cool the powder to room temperature with the furnace to obtain the powder after the second cooling.
[0058] S4. After the powder has been cooled twice, it is ground three times for 3 hours to make it uniformly mixed. Then, a pressure of 12 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0059] S5. The wafer is heated to 1350℃ in air at a heating rate of 3℃ / min and held at that temperature for 22 hours. Finally, it is cooled to room temperature in the furnace to obtain strontium-doped double perovskite oxide ceramic, i.e., Nd... 1.9 Sr 0.1 CoMnO6 ceramic sample.
[0060] Example 3 A strontium-doped double perovskite oxide ceramic Nd 1.8 Sr 0.2 The preparation method of CoMnO6 includes the following steps: S1, according to Nd1.8 Sr 0.2 The stoichiometric ratio of CoMnO6 elements was determined by weighing Nd2O3, Co3O4, MnO2 and SrCO3 with a purity greater than 99.9%, and then grinding them in an agate mortar for 7 hours to obtain a uniformly mixed powder.
[0061] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 950°C at a heating rate of 4°C / min in an air atmosphere and hold for 11 hours for pre-firing. After pre-firing, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0062] S3. Place the cooled powder in an agate mortar and grind it for 5 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat the powder to 1150°C at a heating rate of 4°C / min in an air atmosphere and hold it for 11 hours for a second pre-firing. After the pre-firing is completed, cool the powder to room temperature with the furnace to obtain the powder after the second cooling.
[0063] S4. After the powder has been cooled twice, it is ground three times for 3 hours to make it uniformly mixed. Then, a pressure of 14 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0064] S5. The wafer is heated to 1350℃ in air at a heating rate of 4℃ / min and held at that temperature for 22 hours. Finally, it is cooled to room temperature in the furnace to obtain strontium-doped double perovskite oxide ceramic, i.e., Nd... 1.8 Sr 0.2 CoMnO6 ceramic sample.
[0065] Example 4 A strontium-doped double perovskite oxide ceramic Nd 1.7 Sr 0.3 The preparation method of CoMnO6 includes the following steps: S1, according to Nd 1.7 Sr 0.3 The stoichiometric ratio of CoMnO6 elements was determined by weighing Nd2O3, Co3O4, MnO2 and SrCO3 with a purity greater than 99.9%, and then grinding them in an agate mortar for 8 hours to obtain a uniformly mixed powder.
[0066] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 1000°C at a heating rate of 4°C / min in an air atmosphere and hold for 11 hours for pre-calcination. After pre-calcination, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0067] S3. Place the cooled powder in an agate mortar and grind it for 6 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat the powder to 1200°C at a heating rate of 4°C / min in an air atmosphere and hold it for 11 hours for a second pre-firing. After the pre-firing is completed, cool the powder to room temperature with the furnace to obtain the powder after the second cooling.
[0068] S4. After the powder has been cooled twice, it is ground three times for 3 hours to make it uniformly mixed. Then, a pressure of 14 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0069] S5. The wafer is heated to 1380℃ in air at a heating rate of 4℃ / min and held at that temperature for 22 hours. Finally, it is cooled to room temperature in the furnace to obtain strontium-doped double perovskite oxide ceramic, i.e., Nd... 1.7 Sr 0.3 CoMnO6 ceramic sample.
[0070] Example 5 A strontium-doped double perovskite oxide ceramic Nd 1.6 Sr 0.4 The preparation method of CoMnO6 includes the following steps: S1, according to Nd 1.6 Sr 0.4 The stoichiometric ratio of CoMnO6 elements was determined by weighing Nd2O3, Co3O4, MnO2 and SrCO3 with a purity greater than 99.9%, and then grinding them in an agate mortar for 8 hours to obtain a uniformly mixed powder.
[0071] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 1000°C at a heating rate of 5°C / min in an air atmosphere and hold for 12 hours for pre-firing. After pre-firing, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0072] S3. Place the cooled powder in an agate mortar and grind it for 6 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat the powder to 1200°C at a heating rate of 5°C / min in an air atmosphere and hold it for 12 hours for a second pre-firing. After the pre-firing is completed, cool the powder to room temperature with the furnace to obtain the powder after the second cooling.
[0073] S4. After the powder has been cooled twice, it is ground three times for 4 hours to make it uniformly mixed. Then, a pressure of 16 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0074] S5. The wafer is heated to 1400℃ in air at a heating rate of 5℃ / min and held at that temperature for 24 hours. Finally, it is cooled to room temperature in the furnace to obtain strontium-doped double perovskite oxide ceramic, i.e., Nd... 1.6Sr 0.4 CoMnO6 ceramic sample.
[0075] Example 6 A strontium-doped double perovskite oxide ceramic Nd 1.5 Sr 0.5 The preparation method of CoMnO6 includes the following steps: S1, according to Nd 1.5 Sr 0.5 The stoichiometric ratio of CoMnO6 elements was determined by weighing Nd2O3, Co3O4, MnO2 and SrCO3 with a purity greater than 99.9%, and then grinding them in an agate mortar for 8 hours to obtain a uniformly mixed powder.
[0076] S2. Place the powder from S1 into an alumina crucible and place it in a muffle furnace. Heat the powder to 1050°C at a heating rate of 5°C / min in an air atmosphere and hold for 12 hours for pre-firing. After pre-firing, cool the powder to room temperature with the furnace to obtain the cooled powder.
[0077] S3. Place the cooled powder in an agate mortar and grind it for 6 hours. Then, place it in an alumina crucible and put it in a muffle furnace. Heat the powder to 1250°C at a heating rate of 5°C / min in an air atmosphere and hold it for 12 hours for a second pre-firing. After the pre-firing is completed, cool the powder to room temperature with the furnace to obtain the powder after the second cooling.
[0078] S4. After the powder has been cooled twice, it is ground three times for 4 hours to make it uniformly mixed. Then, a pressure of 16 MPa is applied in the mold to press it into a disc with a diameter of 10 mm and a thickness of 1.5 mm.
[0079] S5. The wafer is heated to 1400℃ in air at a heating rate of 5℃ / min and held at that temperature for 24 hours. Finally, it is cooled to room temperature in the furnace to obtain strontium-doped double perovskite oxide ceramic, i.e., Nd... 1.5 Sr 0.5 CoMnO6 ceramic sample.
[0080] Nd in Examples 1 to 6 above 2-x Sr x CoMnO6 ( x =0.0, x =0.1, x =0.2, x =0.3, x =0.4, x =0.5) The ceramic sample was tested for structure and magnetization properties. In the test result image, the curve of Nd2CoMnO6 in Example 1 is shown as follows. x =0.0, Nd in Example 2 1.9 Sr0.1 The curve representing CoMnO6 in the figure is as follows: x =0.1, Nd in Example 3 1.8 Sr 0.2 The curve representing CoMnO6 in the figure is as follows: x =0.2, Nd in Example 4 1.7 Sr 0.3 The curve representing CoMnO6 in the figure is as follows: x =0.3, Nd in Example 5 1.6 Sr 0.4 The curve representing CoMnO6 in the figure is as follows: x =0.4, Nd in Example 6 1.5 Sr 0.5 The curve representing CoMnO6 in the figure is as follows: x =0.5.
[0081] Figure 1 The XRD patterns of the ceramic samples from Examples 1 to 6 of this invention are shown. Comparison with the standard XRD PDF card (ICDD: 00-020-0760) reveals that the diffraction peaks of the prepared samples are consistent with the double perovskite structure Nd₂CoMnO₆, and the diffraction peaks are sharp, indicating good crystallinity and no second phase formation. The samples possess a single-phase orthogonal structure with space group Pbnm. Furthermore, with the increase of Sr… 2+ Doping amount x The increase, with the main diffraction peaks shifting towards larger angles, indicates that Sr... 2+ Able to completely replace Nd 3+ It enters the Nd₂CoMnO₆ lattice and causes structural distortion. Due to Sr 2+ The ionic radius (1.27 Å) is greater than that of Nd. 3+ Ionic radius (1.08 Å), theoretically Sr 2+ Replace Nd 3+ This should cause lattice expansion, resulting in a shift of diffraction peaks towards lower angles. However, XRD results show the opposite trend, which is consistent with Sr. 2+ Doping and the formation of oxygen vacancy defects caused by high-temperature calcination and Co 2+ Oxidized to Co 3+ Related. Co, which has a large ionic radius. 2+ (0.745 Å) transforms into Co with a smaller ionic radius. 3+ The presence of (0.61 Å) and oxygen vacancy defects leads to lattice contraction, causing the diffraction peaks to shift towards larger angles.
[0082] Figure 2 The O1s XPS spectra and peak division results of the ceramic samples of Examples 1 to 6 of this invention are shown. Figure 2Figure (a) shows the O1s XPS spectrum and peak division results for Example 1; Figure (b) shows the O1s XPS spectrum and peak division results for Example 2; Figure (c) shows the O1s XPS spectrum and peak division results for Example 3; Figure (d) shows the O1s XPS spectrum and peak division results for Example 4; Figure (e) shows the O1s XPS spectrum and peak division results for Example 5; and Figure (f) shows the O1s XPS spectrum and peak division results for Example 6. Figure 2 It can be seen that a relatively large number of oxygen vacancies were formed in the prepared ceramic samples. The formation of oxygen vacancies is related to prolonged high-temperature sintering and low-valence Sr. 2+ Replacement of high-valence Nd 3+ This is related to factors such as temperature and time. For undoped Nd2CoMnO6, during the high-temperature and long-term sintering process, sufficient heat energy breaks some oxygen-oxide bonds and metal-oxide bonds, resulting in lattice relaxation, easy desorption of oxygen atoms, and smooth defect migration, thereby forming oxygen vacancies.
[0083] Table 1 shows the oxygen vacancy content of the ceramic samples obtained by peak separation of the O1s XPS spectrum. As can be seen from Table 1, for Sr... 2+ Doped ceramic samples, when x When Sr ≤ 0.2, as Sr 2+ As the doping concentration increases, the oxygen vacancy content decreases slightly, at which point some Co... 2+ Converted to Co 3+ When 0.2 < x When the oxygen vacancy content is ≤0.5, the oxygen vacancy content increases significantly. To maintain charge balance, low-valence Sr... 2+ Replacing the high-valence state of Nd 3+ This will lead to the formation of more oxygen vacancies. The presence of oxygen vacancies alters the electronic structure, thereby changing the Co content. 2+ / 3+ and Mn 3+ / 4+ The spin structure and magnetic interactions of ions.
[0084] Table 1. Oxygen vacancy content of ceramic samples obtained by peak separation of O1s XPS spectra. Figure 3 These are the Raman spectra of the ceramic samples from Examples 1 to 6 of this invention. Figure 3 It can be seen that for undoped Nd₂CoMnO₆ ceramics, at 475 cm⁻¹... -1 and 628cm -1 The two peaks at the location represent the tensile (AS) and tensile (S) modes of the (Co / Mn)O6 octahedron. For Sr... 2+ In doped ceramics, the intensity of both the AS and S modes decreases significantly with increasing doping concentration, while the peak range broadens considerably. This indicates that Sr... 2+The doping induces significant structural distortion and Co / Mn antisite disorder in the system.
[0085] Next, in order to study Nd 2-x Sr x The magnetic properties of CoMnO6 ceramic samples were measured using a QuantumDesign Dynacool Integrated Physical Property Measurement System (PPMS) for ceramic samples from Examples 1 to 6.
[0086] Figure 4 The graphs show the magnetization intensity of ceramic samples from Examples 1 and 2 of this invention under zero-field cooling and field-cooled conditions when the applied magnetic field is 1 kOe, as a function of temperature. Figure 4 Figure (a) shows the magnetization intensity as a function of temperature in Example 1, and Figure (b) shows the magnetization intensity as a function of temperature in Example 2. Figure 4 It can be seen that under an external magnetic field H At 1 kOe, the magnetization intensity of zero-field cooling (ZFC) and field-cooled (FC) M With temperature T The changes are as follows: As the temperature decreases, Nd2CoMnO6 ceramics at the Curie temperature... T C1 =160K exhibits a long-range ordered paramagnetic-ferromagnetic transition, with the ferromagnetism primarily originating from Co. 2+ -O 2- -Mn 4+ The superexchange effect between them. T C2 The presence of a cluster-like glass transition at 140 K indicates the coexistence of ferromagnetic and antiferromagnetic phases in the low-temperature region. This competitive spin interaction, along with the Co vacancy-induced phase transition, suggests the presence of both ferromagnetic and antiferromagnetic phases at low temperatures. 3+ -O 2- -Mn 3+ Ferromagnetic interactions and Co 3+ -O 2- -Co 3+ Mn 3+ -O 2- -Mn 3+ Antiferromagnetic exchange interaction and magnetic Nd 3+ Related to sublattice. Nell temperature. T N =120K, higher than the temperature of liquid nitrogen (77K). The competition and coexistence of multiple magnetic exchange interactions in the system lead to phase separation, and the coexistence of ferromagnetic and antiferromagnetic phases provides conditions for the exchange bias effect in the system. 2+ Doping amount x The sample with a phase transition temperature of 0.1 (Example 2) exhibited similar magnetization behavior to Nd₂CoMnO₆, but with a slightly lower phase transition temperature.T C1 =157K, T C2 =135K, T N =107K.
[0087] Figure 5 The graphs show the magnetization intensity of ceramic samples from Examples 3 to 6 of this invention under zero-field cooling and field-cooled conditions when the applied magnetic field is 1 kOe, as a function of temperature. Figure 5 Figure (a) shows the magnetization intensity as a function of temperature in Example 3; Figure (b) shows the magnetization intensity as a function of temperature in Example 4; Figure (c) shows the magnetization intensity as a function of temperature in Example 5; and Figure (d) shows the magnetization intensity as a function of temperature in Example 6. Figure 5 It can be seen that under an external magnetic field H At 1 kOe, the magnetization intensity of zero-field cooling (ZFC) and field-cooled (FC) M With temperature T The changes are as follows: with Sr 2+ With increasing doping concentration, Nd 2-x Sr x CoMnO6 ( x =0.2, x =0.3, x =0.4, x =0.5) Co caused by oxygen vacancy defects and antisite disorder in the system 3+ -O 2- -Co 3+ Mn 3+ -O 2- -Mn 3+ Co 2+ -O 2- -Co 2+ Mn 4+ -O 2- -Mn 4+ When antiferromagnetic exchange activity increases, T C1 The long-range magnetic field at the location weakens or even disappears, and the Curie temperature... T C (Right now Figure 4 In T C2 The short-range magnetic order is enhanced at K~128K~141K, therefore T C1 The phase transition at that point gradually disappears with increasing doping concentration. T C ( T C2 The phase transition temperature gradually increases at this point. (Nell temperature) TN All are above liquid nitrogen temperature (77K), and in terms of doping concentration... x After exceeding 0.2, T N The phase transition temperature increases with increasing doping concentration, and the higher temperature increases the practical application value of this system.
[0088] Figure 6 The graphs show the magnetization intensity of ceramic samples from Examples 1 to 6 of this invention under zero-field cooling and field-cooled conditions at 2K as a function of magnetic field. Figure 6 Figure (a) shows the magnetization intensity as a function of magnetic field in Example 1; Figure (b) shows the magnetization intensity as a function of magnetic field in Example 2; Figure (c) shows the magnetization intensity as a function of magnetic field in Example 3; Figure (d) shows the magnetization intensity as a function of magnetic field in Example 4; Figure (e) shows the magnetization intensity as a function of magnetic field in Example 5; and Figure (f) shows the magnetization intensity as a function of magnetic field in Example 6. Figure 6 It can be seen that under zero-field cooling (ZFC) and field cooling (FC) with an applied magnetic field of 1 kOe, the magnetization intensity changes with the magnetic field after cooling from 300 K to 2 K. MH The curves are as follows: for all samples MH All curves exhibit hysteresis, and the maximum magnetization does not reach saturation. Undoped Nd₂CoMnO₆ has a maximum magnetic moment of 58 emu / g under a 70 kOe magnetic field; with Sr… 2+ With increasing doping concentration, the hysteresis gradually weakens, and the maximum magnetization gradually decreases, with the maximum magnetic moment ranging from 35 emu / g to 55 emu / g under a 70 kOe magnetic field. These phenomena indicate that Nd... 2-x Sr x The CoMnO6 system contains both ferromagnetic and antiferromagnetic phases, which change with Sr. 2+ Increased doping concentration weakens ferromagnetic coupling and strengthens antiferromagnetic coupling. The coexistence and competition of ferromagnetic and antiferromagnetic phases provide conditions for the emergence of exchange bias effects in the system. The field-cooled hysteresis loop (FC) towards... H The axis shifts in the negative direction, exhibiting an exchange bias effect. Under a cooling magnetic field of 1 kOe, the exchange bias field of undoped Nd₂CoMnO₆ is 2.8 kOe. The exchange bias phenomenon in undoped Nd₂CoMnO₆ is related to oxygen vacancy defects formed during the high-temperature sintering process. Figure 2 The O1s XPS spectrum analysis results show that the prepared ceramic sample formed a large number of oxygen vacancies. The presence of oxygen vacancies alters the electronic structure, thereby changing the spin structure of the system. Therefore, Co appears in the system. 2+ -O 2- -Co 2+ Co 3+ -O 2- -Co3+ Mn 3+ -O 2- -Mn 3+ Antiferromagnetic exchange interaction with Co 2+ -O 2- -Mn 4+ Co 3+ -O 2- -Mn 3+ The competition and coexistence of ferromagnetic interactions lead to an exchange bias effect in the system. 2+ Replace Nd 3+ The induced changes in the oxygen vacancy defect content in the system, along with the occurrence of Co / Mn antisite disorder, lead to changes in the crystal and magnetic structures. This plays a regulatory role in the competition between ferromagnetic and antiferromagnetic interactions, thereby regulating the exchange bias effect of the system. Under a cooling magnetic field of 1 kOe, the exchange bias field is 2.1 kOe to 3.6 kOe.
[0089] Figure 7 This is a graph showing the exchange bias field and coercivity of the ceramic samples from Examples 1 to 6 of this invention as a function of doping concentration at 2K. Figure 7 It can be seen that the exchange bias field H EB and coercivity H C The size varies with Sr 2+ It changes with the amount of doping. When Sr 2+ As the doping concentration increases, the exchange bias field H EB First increase then decrease, in x Coercivity is at its maximum at 0.4. H C Slightly increased, from x =0.3 and it begins to decrease significantly. Among them H C =∣ H L - H R | / 2, H EB =∣ H L + H R | / 2, H L The point where the hysteresis loop intersects the left side of the horizontal axis. H R This is the intersection of the hysteresis loop and the right side of the horizontal axis.
[0090] Figure 8The images show 10 hysteresis loop diagrams of the ceramic samples from Examples 1 and 4 of this invention, continuously cyclically measured at a temperature of 2K under a cooling magnetic field of 5kOe. Figure 8 Figure (a) is the hysteresis loop diagram of Example 1, and Figure (b) is the hysteresis loop diagram of Example 4. Figure 8 As shown in Figure (a), the hysteresis loops from the 10 measurements coincide, and the exchange bias field does not decrease due to repeated magnetization, meaning no magnetic training effect occurs. This indicates that the uncompensated spin structure at the interface between the ferromagnetic and antiferromagnetic phases is highly stable to the applied external magnetic field. Figure 8 As can be seen in Figure (b), the second cycle is different from the first cycle. H L There is a slight rightward shift, meaning the exchange bias field is somewhat reduced, but in the 2nd to 10th cycles, the hysteresis loops almost overlap, and no significant magnetic training effect reappears. This exchange bias, with no or weak magnetic training effect, avoids the problem of device performance degradation caused by repeated magnetization in practical applications, which is of great significance for practical applications.
[0091] Figure 9 The exchange bias field is obtained by continuously cyclically measuring the hysteresis loop 10 times under a cooling magnetic field of 5 kOe at a temperature of 2 K for the ceramic samples of Examples 1 and 4 of this invention. H EB A graph showing the relationship between the number of measurements (n) and the measurement frequency (n). Figure 9 It can be seen that, for x =0.0 sample, exchange bias field H EB The value remains constant with increasing cycle number n, indicating that there is no magnetic training effect; for x =0.3 samples, the bias field was exchanged between the first and second cycles. H EB Reduce by 3.2%, repeat until the 10th cycle. H EB The 4.5% reduction indicates that the exchange bias has a weak magnetic training effect, which is almost negligible.
[0092] In summary, the Nd double perovskite ceramic material provided by this invention... 2-x Sr x CoMnO6 (0≤ x ≤0.5) exhibits a significant exchange bias effect, and this exchange bias system shows almost no magnetic training effect. By changing Sr 2+ The amount of doping can effectively control the magnetic properties and exchange bias field of a material, thus meeting the needs of different applications.
[0093] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.
[0094] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.
Claims
1. A double perovskite oxide ceramic with exchange bias effect, characterized in that, The chemical formula of the double perovskite oxide ceramic is Nd 2-x Sr x CoMnO6, of which Sr 2+ For doped ions, molar doping amount x 0.0≤ x ≤0.5; The double perovskite oxide ceramic has a single-phase orthogonal structure; when x When ω = 0.0, the chemical formula of the double perovskite oxide ceramic is Nd₂CoMnO₆. The double perovskite oxide ceramic exhibits an exchange bias effect, and this exchange bias has no magnetic tempering effect; when 0.0 < ω, the chemical formula is Nd₂CoMnO₆. x When Sr ≤ 0.5 2+ The crystal structure and spin structure of the doping-induced system change, thereby controlling the magnetic order type, phase transition temperature and exchange bias field.
2. The double perovskite oxide ceramic with exchange bias effect according to claim 1, characterized in that, When Sr 2 + molar doping amount x The Curie temperature of Nd2CoMnO6 when it is 0.0 T C1 For 160K, T C2 At 140K, under a magnetic field of 70kOe, the maximum magnetic moment is 58 emu / g, and under a cooling magnetic field of 1kOe, the exchange bias field is 2.8kOe; when Sr 2+ molar doping amount x 0.0 < x When ≤0.5, in T C1 The paramagnetic-ferromagnetic phase transition that occurs gradually disappears with increasing doping concentration, and the Curie temperature... T C2 The range is 128K~141K. Under a magnetic field of 70kOe, the maximum magnetic moment is 35emu / g~55emu / g. Under a cooling magnetic field of 1kOe, the exchange bias field is 2.1kOe~3.6kOe.
3. A method for preparing a double perovskite oxide ceramic with exchange bias effect as described in claim 1 or claim 2, characterized in that, Includes the following steps: Neodymium oxide, cobalt oxide, manganese dioxide, and strontium carbonate were weighed according to the stoichiometric ratio to obtain a mixture; Using the mixture as raw material, the mixture is ground and then pre-fired in air to obtain the first pre-fired product; Using the first pre-calcined product as raw material, the product is ground and then pre-calcined a second time under air to obtain the second pre-calcined product; Using the second pre-calcination product as raw material, the material was ground, compressed into tablets, and then calcined in air to form a single-phase orthogonal structure, yielding Nd. 2-x Sr x CoMnO6 is a double perovskite oxide ceramic with exchange bias effect.
4. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, The first pre-firing temperature is 900℃~1050℃, and the time is 10h~12h.
5. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, The second pre-firing temperature is 1100℃~1250℃, and the time is 10h~12h.
6. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, The calcination temperature is 1350℃~1400℃, and the time is 20h~24h.
7. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, The heating rates for the first pre-firing, the second pre-firing, and the calcination were all 3℃ / min to 5℃ / min.
8. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, The tablet compression pressure is 10MPa~16MPa.
9. The method for preparing the double perovskite oxide ceramic with exchange bias effect according to claim 3, characterized in that, After the first pre-firing, the second pre-firing, and the calcination, the cooling method was to cool the furnace to room temperature.