Ferromagnetic strong insulating material and method for producing same

Abstract

The application provides a ferromagnetic strong insulating material, which has a chemical formula of CaCu3Mn2Te2O 12 The application also provides a method for preparing the ferromagnetic strong insulating material, which comprises the following steps: (1) grinding and mixing CaO, CuO, MnO2 and TeO2 in a protective gas atmosphere to obtain a mixture; (2) sealing the mixture obtained in the step (1) and then performing a heating and pressurizing treatment; and (3) optionally, cooling and depressurizing the treatment product obtained in the step (2). The ferromagnetic strong insulating material has both ferromagnetism and strong insulation. The Curie temperature of the ferromagnetic strong insulating material is 99.8K, the saturation magnetization at 2K temperature is 5.50μ B ·fu ‑1 , and the optical band gap is 5.05eV. The material has potential value and application prospect in future spin electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of materials science. Specifically, this invention relates to a ferromagnetic insulating material and its preparation method. Background Technology

[0002] Ferromagnetic refers to a magnetic state in which materials can be strongly attracted by permanent magnets. This strong magnetism originates from the parallel alignment of spins within the material, where the parallel spins generate spontaneous magnetization. Ferromagnetic in a broader sense also includes ferrimagnetism, in which unequal antiparallel spins exist.

[0003] The ferromagnetism of materials typically originates from double exchange interactions, in which electron transitions are real, thus ferromagnetism is often accompanied by metallic properties. In other words, ferromagnetic materials are generally metallic conductors, such as CrO2. However, ferromagnetism and insulation are rarely found simultaneously in a single material. Therefore, the search for materials that possess both ferromagnetism and insulation properties—that is, ferromagnetic insulators—has been a persistent pursuit for researchers.

[0004] Ferromagnetic insulators not only possess profound physical implications but also hold broad application prospects in spintronic devices. Compared to traditional magnetic materials, ferromagnetic insulators contain only magnetons and no electric charge. The information carried by the spin propagates solely through magnetons, thus avoiding unnecessary power losses caused by charge transport. Therefore, ferromagnetic insulators are frequently used in spintronics research, such as the spin Hall magnetoresistance effect and the spin Seebeck effect.

[0005] Currently known ferromagnetic insulator materials include: Y3Fe5O 12 Fe3O4, BaFe 12 O 19 K2Cr8O 16 EuS, etc. However, these known ferromagnetic insulators typically have small optical band gaps. Y3Fe5O 12 The optical band gap is approximately 2.85 eV, while BaFe 12 O 19 The optical band gaps of Fe3O4 and Fe3O4 are even smaller, at 1.8 eV and 0.12 eV, respectively. For insulators with very small optical band gaps, thermal fluctuations at room temperature are sufficient to excite electrons from the valence band to the conduction band. In this case, the insulator becomes a semiconductor, and the increased conductivity makes it unsuitable for spintronic devices. Conversely, a larger optical band gap indicates that it is more difficult for electrons at the top of the valence band to be thermally excited to the conduction band, making the material less conductive and more advantageous for applications.

[0006] Therefore, exploring ferromagnetic strong insulating materials is essential. Currently, there is an urgent need for a ferromagnetic strong insulating material with a large optical band gap. Summary of the Invention

[0007] Therefore, the purpose of this invention is to provide a new ferromagnetic insulating material with a large optical band gap.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution.

[0009] On the one hand, the present invention provides a ferromagnetic insulating material with the chemical formula CaCu3Mn2Te2O 12 .

[0010] Preferably, in the ferromagnetic insulating material described in this invention, a Cu target K is used. α1 The X-ray powder diffraction pattern, expressed in 2θ angles, shows diffraction peaks at 20.23°, 33.33°, 39.29°, 47.85°, 52.45°, and 59.56°, with a 2θ angle measurement error of ±0.005°.

[0011] Preferably, in the ferromagnetic insulating material described in this invention, a Cu target K is used. α1 The X-ray powder diffraction pattern, expressed in 2θ angles, shows diffraction peaks at 23.40°, 28.76°, 37.39°, 44.58°, 53.93°, 70.00°, and 79.77°, with a 2θ angle measurement error of ±0.005°.

[0012] Preferably, in the ferromagnetic insulating material of the present invention, the space group of the ferromagnetic insulating material is Pn-3, and the lattice constant a is...

[0013] Preferably, in the ferromagnetic insulating material of the present invention, the Curie temperature of the ferromagnetic insulating material is 99.8K.

[0014] Preferably, in the ferromagnetic insulating material of the present invention, the ferromagnetic insulating material has a saturation magnetization of 5.50 μ at a temperature of 2 K. B ·fu -1 .

[0015] Preferably, in the ferromagnetic insulating material of the present invention, the optical band gap of the ferromagnetic insulating material is 5.05 eV.

[0016] On the other hand, the present invention provides a method for preparing the ferromagnetic insulating material described herein, which includes the following steps:

[0017] (1) CaO, CuO, MnO2 and TeO2 are thoroughly ground and mixed in a protective gas atmosphere to obtain a mixture;

[0018] (2) After sealing and wrapping the mixture obtained in step (1), heat and pressurize it;

[0019] (3) Optionally, the processed product obtained in step (2) is cooled and depressurized.

[0020] Preferably, in the method described in this invention, the molar ratio of CaO, CuO, MnO2 and TeO2 in step (1) is CaO:CuO:MnO2:TeO2 = 1:3:2:2.

[0021] Preferably, in the method described in this invention, the protective gas is selected from one or more of nitrogen, helium, and argon.

[0022] Preferably, in the method described in this invention, the grinding in step (1) is carried out by grinding in an agate mortar for 15 minutes to 2 hours.

[0023] Preferably, in the method described in this invention, the treatment in step (2) is carried out under the following conditions: temperature of 1073-1473K, pressure of 8-12GPa, and time of 30 minutes to 2 hours.

[0024] Preferably, in the method described in this invention, the sealing and wrapping in step (2) is performed using a gold capsule or a platinum capsule.

[0025] Preferably, in the method described in this invention, the gold capsule or platinum capsule is cylindrical.

[0026] Preferably, in the method described in this invention, the gold capsule or platinum capsule has a diameter of 2-10 mm, a height of 2-10 mm, and a thickness of 0.1-1 mm.

[0027] Preferably, in the method described in this invention, the processing in step (2) is carried out in a six-sided top press or a 6-8 type two-stage push press.

[0028] Preferably, in the method of the present invention, the cooling in step (3) is carried out by cooling the product to room temperature over 30 seconds to 5 hours.

[0029] Preferably, in the method of the present invention, the depressurization in step (3) is carried out by reducing the product to ambient pressure within 5-12 hours.

[0030] The present invention has the following beneficial effects:

[0031] The CaCu3Mn2Te2O provided by this invention 12This is a novel ferromagnetic strong insulating material, which unusually possesses both ferromagnetism and strong insulation properties. The ferromagnetic strong insulating material of this invention is CaCu3Mn2Te2O. 12 The Curie temperature is 99.8 K, and the saturation magnetization at 2 K is 5.50 μ. B ·fu -1 The optical bandgap is 5.05 eV. This material has potential value and application prospects in future spintronic devices. Attached Figure Description

[0032] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, wherein:

[0033] Figure 1 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 XRD patterns;

[0034] Figure 2 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 A schematic diagram of the crystal structure;

[0035] Figure 3 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 X-ray absorption spectrum;

[0036] Figure 4 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 The curves showing the changes in magnetic susceptibility and specific heat with temperature;

[0037] Figure 5 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 The curve of magnetization intensity as a function of magnetic field strength;

[0038] Figure 6 The present invention relates to the ferromagnetic insulating material CaCu3Mn2Te2O 12 A schematic diagram of the optical bandgap. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0040] Example 1

[0041] CaO (purity >99.9%), CuO (purity >99.9%), MnO2 (purity >99.9%), and TeO2 (purity >99.9%) were mixed in a molar ratio of 1:3:2:2. The mixture was then ground for 1 hour in an argon-filled glove box using an agate mortar to ensure thorough mixing. This mixture was then filled into platinum capsules with a diameter of 3 mm, a height of 5 mm, and a thickness of 0.1 mm and sealed. The resulting platinum capsules were placed in a six-sided press. The reaction mixture was allowed to react within the platinum capsules for 30 minutes at a pressure of 8 GPa and a temperature of 1373 K to obtain the reaction product. The reaction product was cooled to room temperature within 30 seconds, and the pressure was slowly released over 10 hours. Finally, the reaction product was removed from the platinum capsules to obtain CaCu3Mn2Te2O. 12 .

[0042] Figure 1 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 XRD patterns.

[0043] Figure 2 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 A schematic diagram of the crystal structure. (See diagram below.) Figure 2 As shown, the CaCu3Mn2Te2O prepared in Example 1 of this invention 12 It is a tetrahedral perovskite structure with simultaneous ordering at both A and B sites, space group Pn-3, and lattice constant a. The CaCu3Mn2Te2O prepared in Example 1 of this invention 12 Cu at site A' 2+ The ion has planar quadrilateral coordination, with Mn at both B-site and B'-site. 2+ Ions and Te 6+ The ion has octahedral coordination, and Mn at the B site 2+ Te ions and B' sites 6+ Ions form an ordered structure in rock salt.

[0044] Figure 3 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 The X-ray absorption spectrum. Characteristic absorption peaks in X-ray absorption spectra are sensitive to elements and can reflect the valence state of the elements. For example... Figure 3 As shown, the CaCu3Mn2Te2O prepared in Example 1 of this invention 12 The peak positions and spectral shapes of the L3 and L2 absorption peaks of Cu in the reference Cu are compared with those of Cu in the reference Cu. 2+ O is very similar, which means that the CaCu3Mn2Te2O prepared in Example 1 of this invention is very similar. 12The oxidation state of Cu in the sample is +2. The CaCu3Mn2Te2O prepared in Example 1 of this invention... 12 The peak positions and spectral shapes of the L3 and L2 absorption peaks of Mn compared with those of the reference Mn 2+ O is very similar, which means that the CaCu3Mn2Te2O prepared in Example 1 of this invention is very similar. 12 The valence state of Mn is +2.

[0045] Figure 4 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 The curves showing the changes in magnetic susceptibility and specific heat with temperature. For example... Figure 4 As shown, with decreasing temperature, the CaCu3Mn2Te2O prepared in Example 1 of this invention... 12 The magnetic susceptibility increases rapidly at 96 K, and the specific heat data shows a significant λ-type anomaly at 99.8 K. This means that the CaCu3Mn2Te2O prepared in Example 1 of this invention... 12 It undergoes a ferromagnetic phase transition at 99.8 K, with a Curie temperature of 99.8 K.

[0046] Figure 5 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 The curve showing the change in magnetization intensity as a function of magnetic field strength. For example... Figure 5 As shown, at a temperature of 2K, the CaCu3Mn2Te2O prepared in Example 1 of this invention... 12 It exhibits typical ferromagnetic behavior, with a saturation magnetization of 5.50 μ. B ·fu -1 .

[0047] Figure 6 The ferromagnetic insulating material CaCu3Mn2Te2O prepared in Example 1 of this invention 12 A schematic diagram of the optical bandgap. (See diagram below.) Figure 6 As shown, the CaCu3Mn2Te2O prepared in Example 1 of this invention was obtained according to the Tauc model. 12 The optical band gap is 5.05 eV. Such a large optical band gap indicates that the CaCu3Mn2Te2O prepared in Example 1 of this invention has a high optical band gap. 12 It possesses strong insulating properties. This is because the CaCu3Mn2Te2O prepared in Example 1 of this invention... 12 Middle B position Mn 2+ Te ions and B' sites 6+ (d 10 The ions form an ordered structure in the rock salt, which prevents the formation of conductive channels.

[0048] Example 2

[0049] CaO (purity >99.9%), CuO (purity >99.9%), MnO2 (purity >99.9%), and TeO2 (purity >99.9%) were mixed in a molar ratio of 1:3:2:2. The mixture was then ground for 2 hours in an argon-filled glove box using an agate mortar to ensure thorough mixing. This mixture was then filled into gold capsules with a diameter of 3 mm, a height of 4 mm, and a thickness of 0.1 mm and sealed. The resulting gold capsules were placed in a six-sided press. The reaction mixture was allowed to react within the gold capsules for 45 minutes at a pressure of 9 GPa and a temperature of 1273 K to obtain the reaction product. The reaction product was cooled to room temperature within 30 seconds, and the pressure was slowly released over 11 hours. Finally, the reaction product was removed from the gold capsules to obtain CaCu3Mn2Te2O. 12 .

[0050] The ferromagnetic insulating material CaCu3Mn2Te2O prepared in this embodiment 12 The structure and performance are the same as in Example 1.

[0051] Example 3

[0052] CaO (purity >99.9%), CuO (purity >99.9%), MnO2 (purity >99.9%), and TeO2 (purity >99.9%) were mixed in a molar ratio of 1:3:2:2. The mixture was then ground for 30 minutes in an argon-filled glove box using an agate mortar to ensure thorough mixing. This mixture was then filled into platinum capsules with a diameter of 3 mm, a height of 5 mm, and a thickness of 0.1 mm and sealed. The resulting platinum capsules were placed in a six-sided press. The reaction mixture was allowed to react within the platinum capsules for 1 hour at a pressure of 10 GPa and a temperature of 1473 K to obtain the reaction product. The reaction product was cooled to room temperature within 30 seconds, and the pressure was slowly released over 12 hours. Finally, the reaction product was removed from the platinum capsules to obtain CaCu3Mn2Te2O. 12 .

[0053] The ferromagnetic insulating material CaCu3Mn2Te2O prepared in this embodiment 12 The structure and performance are the same as in Example 1.

Claims

1. A ferromagnetic insulating material with the chemical formula CaCu3Mn2Te2O 12 ,in, Using Cu target K α1 The X-ray powder diffraction pattern, expressed in 2θ angles, shows diffraction peaks at 20.23°, 23.40°, 28.76°, 33.33°, 37.39°, 39.29°, 44.58°, 47.85°, 52.45°, 53.93°, 59.56°, 70.00°, and 79.77°. The measurement error of the 2θ angle is ±0.005°.

2. The ferromagnetic insulating material according to claim 1, wherein, The space group of the ferromagnetic insulating material is Pn-3, and the lattice constant a is 7.59338 Å.

3. The ferromagnetic insulating material according to claim 1, wherein, The Curie temperature of the ferromagnetic insulating material is 99.8 K.

4. The ferromagnetic insulating material according to claim 1, wherein, The ferromagnetic insulating material has a saturation magnetization of 5.50 μ at 2 K. B ·fu -1 .

5. The ferromagnetic insulating material according to claim 1, wherein, The optical band gap of the ferromagnetic insulating material is 5.05 eV.

6. A method for preparing a ferromagnetic insulating material according to any one of claims 1-5, comprising the following steps: (1) CaO, CuO, MnO2 and TeO2 are thoroughly ground and mixed in a protective gas atmosphere to obtain a mixture; (2) After sealing and wrapping the mixture obtained in step (1), heat and pressurize it; (3) Cool and depressurize the processed product obtained in step (2). In step (1), the molar ratio of CaO, CuO, MnO2 and TeO2 is CaO:CuO:MnO2:TeO2=1:3:2:2; The protective gas is selected from one or more of nitrogen, helium, and argon; The treatment in step (2) is carried out under the following conditions: temperature of 1073-1473 K, pressure of 8-12 GPa, and time of 30 minutes to 2 hours; The cooling in step (3) is carried out by reducing the product to room temperature over 30 seconds to 5 hours; The depressurization in step (3) is carried out by reducing the product to ambient pressure over 5-12 hours.

7. The method according to claim 6, wherein, The grinding in step (1) is carried out by grinding in an agate mortar for 15 minutes to 2 hours.

8. The method according to claim 6, wherein, The sealing and wrapping in step (2) is done using gold capsules or platinum capsules.

9. The method according to claim 8, wherein, The gold or platinum capsules are cylindrical.

10. The method according to claim 8, wherein, The gold or platinum capsule has a diameter of 2-10 mm, a height of 2-10 mm, and a thickness of 0.1-1 mm.

11. The method according to claim 6, wherein, The processing in step (2) is carried out in a six-sided top press or a 6-8 type two-stage push press.

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