Preparation Method of a Ternary Magnetic Selenide and Its Single Crystal

Abstract

The present invention discloses a preparation method of a ternary magnetic selenide and its single crystal, which relates to the technical field of crystal material preparation. The chemical formula of the ternary magnetic selenide is VCrSe3, which can be prepared by chemical vapor transport method using a specific ratio of vanadium source, chromium source and selenium source as raw materials and iodine source as a transport agent; the crystal structure of the VCrSe3 single crystal is monoclinic phase ( I 2 / m ), and an antiferromagnetic to ferromagnetic phase transition and spin reorientation occur at low temperature, so it has application potential in the fields of spintronics, optoelectronics, etc.; the large-size and high-quality VCrSe3 single crystal prepared by the present invention can provide materials for the study of its intrinsic physical properties and the development of functional devices such as optoelectronic devices and spintronics.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal materials, and particularly relates to a ternary magnetic selenide and a preparation method thereof for single crystals. Background Art

[0002] In recent years, electronic devices have been continuously developing towards miniaturization and high integration. Traditional electronics is based on the degree of freedom of electron charge, and there are bottleneck problems such as heat dissipation and stability. Spin electronics (also known as magnetoelectronics) based on the spin property of electrons has developed rapidly. Magnetic transition metal chalcogenides have many novel physical properties, such as high carrier mobility, high optoelectronic conversion efficiency, and magnetism, becoming a research hotspot in the fields of condensed matter physics and materials, and having good application prospects in the fields of optoelectronic devices, non-volatile memories, and spin electronic devices.

[0003] Currently, the research objects of magnetic transition metal chalcogenides are mainly binary transition metal chalcogenides, such as the reported Cr x X y (X = S, Se, Te), or magnetic transition metal chalcogenides introduced by element intercalation or doping. Among them, for chromium-based magnetic selenides, the Chinese invention patent with the publication number CN 118653214 B discloses "a preparation method of a vanadium-doped layered selenide and its single crystal", specifically discloses regulating the electrical transport properties of Cr2Se3 by vanadium doping. However, the characteristic of the magnetic phase transition of the material does not appear in the curve of the resistance varying with temperature, indicating that vanadium doping does not significantly change the antiferromagnetic magnetic properties of Cr2Se3 at low temperatures; in addition, since the doping concentration is a range value, it is not easy to control during actual preparation, and problems such as point defects are likely to be introduced; at the same time, the performance of the material is affected by the content of element doping, which is not conducive to obtaining materials with stable electromagnetic properties.

[0004] It can be seen that the existing technology still needs to be further improved and enhanced. Summary of the Invention

[0005] In view of the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a ternary magnetic selenide and a preparation method thereof for single crystals, aiming to solve the defect of insufficient magnetotransport properties of the vanadium-doped selenide V x Cr 2-x Se3 (0 < x ≤ 0.25) at low temperatures.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A ternary magnetic selenide, wherein the chemical formula of the selenide is VCrSe3, and its crystal structure is monoclinic phase I 2 / m .

[0008] A method for preparing a ternary magnetic selenide single crystal as described above, wherein the ternary magnetic selenide is the ternary magnetic selenide as described above; the method uses vanadium powder, chromium powder, and selenium powder with a molar ratio of 1:1:3 as raw materials, uses iodine particles as a transport agent, and obtains a ternary magnetic selenide single crystal through high-temperature firing and transport growth in a two-temperature zone.

[0009] In the method for preparing the ternary magnetic selenide single crystal, the method includes the steps of: taking vanadium powder, chromium powder, selenium powder, and iodine particles, mixing them evenly, sealing them in a quartz tube, and making the vacuum degree in the quartz tube ≤ 1 Pa. Place the end of the quartz tube with the material in the high-temperature zone of a two-temperature furnace, and the end without the material in the low-temperature zone of the two-temperature furnace; heat up, make the temperature at the low-temperature zone end be 900 ± 25 °C, and the temperature at the high-temperature zone end be 1000 ± 25 °C. Keep the temperature for 5 - 10 days under this temperature condition, then cool to room temperature, and after cleaning and drying, obtain a ternary magnetic selenide single crystal.

[0010] Beneficial effects:

[0011] The present invention provides a ternary magnetic selenide with the chemical formula VCrSe3 and a monoclinic crystal structure. I 2 / m It is an intrinsically magnetically ordered transition metal chalcogenide crystal and has a definite molecular structural formula and stoichiometric ratio. Therefore, the performance of the compound is stable. Moreover, through the study of the magnetic transport properties of this selenide, it is found that this selenide has magnetism at low temperatures, so it has application potential in the fields of spintronics, optoelectronics, etc.

[0012] The second aspect of the present invention also provides a method for preparing a ternary magnetic selenide single crystal. By using a specific molar ratio of raw materials and a growth environment in a two-temperature zone, the controllable synthesis of a large-sized and high-quality ternary magnetic selenide VCrSe3 single crystal is realized, providing materials for the physical property research and the fabrication of functional devices of such materials. Brief description of the drawings

[0013] Figure 1 It is an optical photograph of the VCrSe3 single crystal in Example 1.

[0014] Figure 2 It is an X-ray diffraction analysis pattern of the VCrSe3 single crystal in Example 1.

[0015] Figure 3 It is an X-ray diffraction analysis pattern of the VCrSe3 powder in Example 1.

[0016] Figure 4 It is a surface morphology diagram of the VCrSe3 single crystal in Example 1.

[0017] Figure 5 It is the energy spectrum diagram of the VCrSe3 single crystal in Example 1.

[0018] Figure 6 It is the atomic resolution structure diagram of the VCrSe3 single crystal in the

[010] projection direction in Example 1.

[0019] Figure 7 It is the curve graph of the magnetic susceptibility of the VCrSe3 sample in Example 1 varying with temperature at 500 Oe (zero field cooling ZFC, applied magnetic field B = 500 Oe) and the first derivative graph of the magnetization varying with temperature.

[0020] Figure 8 It is the curve graph of the magnetization of the VCrSe3 sample in Example 1 varying with the magnetic field at different temperatures.

[0021] Figure 9 It is the optical photograph of the VCrSe3 single crystal in Comparative Example 3. Detailed implementation manners

[0022] The present invention provides a preparation method of a ternary magnetic selenide and its single crystal. To make the purpose, technical solution and effect of the present invention clearer and more definite, the following examples are given to further illustrate the present invention in detail. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0023] In the prior art, due to the vanadium-doped layered V x Cr 2-x Se3 (0 < x ≤ 0.25) can regulate the electrical transport properties of the material. However, since its doping concentration is a variable and the properties of the material are affected by the element doping content, it is not conducive to obtaining a material with stable electromagnetic properties, and the antiferromagnetic magnetic characteristics of the material at low temperature are not significantly changed after doping.

[0024] In view of the foregoing problems, the present invention discloses a ternary magnetic selenide, the chemical formula of which is VCrSe3, and its crystal structure is monoclinic phase ( I 2 / m ), which is an intrinsically magnetic-ordered transition metal chalcogenide crystal. Moreover, this compound has a definite molecular structural formula and stoichiometric ratio, so the properties of the compound are stable. Through the study of the magnetic transport properties of this selenide, it is found that within the test temperature range of 2 - 300 K (such as Figure 7As shown in the figure, the selenide undergoes two magnetic property transitions at low temperatures. Among them, in the temperature range from room temperature to 35 K, the selenide exhibits antiferromagnetic characteristics; as the temperature decreases to around 35 K, its antiferromagnetic phase transforms into a ferromagnetic phase; when the temperature continues to decrease to around 10 K, spin reorientation occurs within the selenide. Thus, it can be seen that the selenide has an obvious hysteresis loop at low temperatures and shows the phenomenon of high-field non-saturation, indicating that the selenide has magnetism at low temperatures. Therefore, this magnetically ordered atomic crystal can provide a basis for studying single-crystal magnetic ground states, elementary excitations, and magnon dynamics, and has application potential in the fields of spintronics, optoelectronics, etc.

[0025] The second aspect of the present invention also provides a method for preparing the ternary magnetic selenide single crystal. The method uses vanadium powder, chromium powder, and selenium powder with a molar ratio of 1:1:3 as raw materials, and iodine particles as a transport agent. Through high-temperature firing and transport growth in a two-temperature zone, the ternary magnetic selenide single crystal as described above is obtained. This preparation method has simple steps and is easy to implement. With raw materials in a specific ratio in a furnace body with a two-temperature zone, it can be achieved through a vapor transport method, and the prepared crystal is a large-size and high-quality single crystal, providing materials for subsequent research on the ternary magnetic selenide.

[0026] In this preparation method, the mass purity of the vanadium powder, chromium powder, selenium powder, and iodine particles is all ≥99.99% to reduce the influence of impurities on crystal formation; at the same time, the addition concentration of iodine particles is controlled at 10 mg / mL to make it have better transport performance and make the subsequent cleaning of the crystal easier.

[0027] As an optimized scheme, the method for preparing the ternary magnetic selenide single crystal specifically includes the following steps: Take vanadium powder, chromium powder, and selenium powder according to a molar ratio of 1:1:3, mix them evenly and place them in a quartz tube, add iodine particles with a concentration of 10 mg / mL, evacuate and make the vacuum degree in the quartz tube ≤1 Pa, and seal the quartz tube; Place the end of the quartz tube with the material in the high-temperature zone of the two-temperature furnace, and the end without the material in the low-temperature zone of the two-temperature furnace; Raise the temperature so that the temperature at the low-temperature zone end is 900 ± 25 °C, and the temperature at the high-temperature zone end is 1000 ± 25 °C. Keep the temperature gradient for 5 - 10 days, then cool to room temperature, and after cleaning and drying, obtain the ternary magnetic selenide single crystal.

[0028] The ternary magnetic selenide single crystal prepared by this method, as Figure 1 shown, has a relatively large size and can provide materials for the study of its physical and chemical properties.

[0029] To further elaborate on a ternary magnetic selenide single crystal and its preparation method provided by the present invention, the following examples are provided.

[0030] Example 1

[0031] A method for preparing a ternary magnetic selenide single crystal comprises the following steps:

[0032] Step 1: Ingredients and packaging

[0033] Using 99.99% vanadium powder, 99.99% chromium powder, 99.99% selenium powder, and 99.99% iodine particles with a mass purity of 1:1:3 as raw materials, the vanadium powder, chromium powder, and selenium powder are mixed in a quartz tube at a molar ratio of 1:1:3, and 10 mg / mL iodine particles are added; the vacuum is evacuated to ≤1Pa, and then the quartz tube containing the raw material sample is sealed using a flame sealing device.

[0034] Step 2: Dual-temperature zone high temperature firing

[0035] The vacuum-sealed quartz tube was placed flat in a dual-zone tube furnace. The raw materials were concentrated at one end of the quartz tube, which was placed at the thermocouple at the high-temperature zone end of the dual-zone tube furnace. The tip of the quartz tube was placed at the thermocouple at the low-temperature zone end. The temperature at the low-temperature zone end was controlled at 875 °C, and the temperature at the high-temperature zone end was controlled at 975 °C. The temperature was raised from room temperature to the specified temperature over 390 min, and the temperature was kept at this temperature gradient for 5 days. Subsequently, the vacuum-sealed quartz tube was naturally cooled to room temperature. The grown material was placed in alcohol, washed and dried to obtain a ternary magnetic selenide single crystal with the chemical formula VCrSe3.

[0036] The material prepared in Example 1 was characterized and analyzed by optical microscope, X-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, and spherical aberration corrected transmission electron microscope. The results are as follows: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 As shown. Among them, Figure 1 This is an optical photograph of the material prepared in Example 1 taken through an optical microscope. Figure 1 It can be seen that the size of this material is close to 1 cm, which is a large size; Figure 2 This is the X-ray diffraction analysis spectrum of the material prepared in Example 1, Figure 3 The X-ray diffraction analysis spectrum of the powder of the material prepared in Example 1 is Figure 2 and Figure 3 It can be seen that the material prepared by this method is a single crystal material; Figure 4 is the surface morphology of the single crystal material. Figure 5 is the energy spectrum of the single crystal material, Figure 6This is the atomic resolution structure diagram of the single crystal material along the

[010] projection direction. Therefore, through the analysis and characterization of the surface morphology, crystal structure, and chemical composition of this material, it can be determined that the material obtained by this preparation method is a single crystal, its growth orientation is the (00l) direction, the chemical composition is VCrSe3, and the microscopic morphology presents an obvious striped orientation structure. Combining X-ray diffraction and electron microscopy analysis, it can be determined that the crystal structure of VCrSe3 is monoclinic phase ( I2 / m )

[0037] In addition, the magnetic transport properties of the obtained material were characterized by a superconducting quantum interference device. The magnetization of the material sample was measured as a function of temperature (zero-field cooling ZFC, applied magnetic field B = 500 Oe), and the first derivative change graph of magnetization with temperature was plotted. The results are as Figure 7 shown. From Figure 7 it can be seen that within the test temperature range of 2 - 300 K, the sample undergoes two magnetic property transitions at low temperatures. Among them, from room temperature to 35 K, the sample exhibits antiferromagnetic characteristics; as the temperature decreases to about 35 K, the antiferromagnetic phase transforms into a ferrimagnetic phase; when the temperature continues to decrease to about 10 K, a spin reorientation occurs within the sample. In addition, the variation of magnetization with magnetic field strength of VCrSe3 at different temperatures was also measured, as specifically shown in Figure 8 shown. From Figure 8 it can be seen that VCrSe3 has an obvious hysteresis loop at low temperatures and shows a phenomenon of high-field non-saturation, indicating that the sample has magnetism at low temperatures.

[0038] Example 2

[0039] Step 1: Ingredient preparation and encapsulation

[0040] Using vanadium powder with a mass purity of 99.99%, chromium powder with a mass purity of 99.99%, selenium powder with a mass purity of 99.99%, and iodine particles with a mass purity of 99.99% as raw materials, vanadium powder, chromium powder, and selenium powder with a molar ratio of 1:1:3 were mixed and placed in a quartz tube, and iodine particles with a concentration of 10 mg / mL were added; the vacuum was pumped to ≤1 Pa, and then the quartz tube containing the raw material sample was sealed using a flame sealing device.

[0041] Step 2: High-temperature firing in a two-temperature zone

[0042] The vacuum-sealed quartz tube was placed flat in a dual-zone tube furnace. The raw materials were concentrated at one end of the quartz tube, which was placed at the thermocouple at the high-temperature end of the dual-zone tube furnace. The tip of the quartz tube was placed at the thermocouple at the low-temperature end. The temperature at the low-temperature end was controlled at 900 °C, and the temperature at the high-temperature end was controlled at 1000 °C. The temperature was raised from room temperature to the specified temperature over 390 min, and the temperature was kept at this temperature gradient for 7 days. Subsequently, the vacuum-sealed quartz tube was naturally cooled to room temperature. The grown material was placed in alcohol, washed and dried to obtain a ternary magnetic selenide single crystal with the chemical formula VCrSe3.

[0043] The material prepared in Example 2 was characterized by optical microscopy, X-ray diffractometer and scanning electron microscopy for morphology, structure and chemical composition. It was determined that the material obtained under this condition was a single crystal with a chemical formula of VCrSe3 and a monoclinic crystal structure ( I2 / m ).

[0044] Comparative Example 1

[0045] A method for preparing selenide, wherein the preparation steps are substantially the same as those of Example 1, except that in step 1, the molar ratio of vanadium powder, chromium powder and selenium powder is 1:2:3.

[0046] After the reaction was completed, it was found that no obvious single crystals were formed in the low temperature region, indicating that the corresponding single crystals could not be obtained under this temperature condition and raw material molar ratio.

[0047] Comparative Example 2

[0048] A method for preparing selenide, wherein the preparation steps are substantially the same as those of Example 1, except that in step 2, the temperature at the low temperature zone end is 800° C., and the temperature at the high temperature zone end is 900° C.

[0049] After the reaction, it was found that no single crystal was formed in the low temperature zone. The reason may be that the temperatures of the low temperature zone and the high temperature zone in Comparative Example 2 were relatively low, and the gas phase transport process was not easy to occur, resulting in no obvious single crystal formation at the low temperature zone end under the experimental conditions.

[0050] Comparative Example 3

[0051] Step 1: Ingredients and packaging

[0052] Using 99.99% vanadium powder, 99.99% chromium powder, 99.99% selenium powder, and 99.99% iodine particles with a mass purity of 1:1:3 as raw materials, vanadium powder, chromium powder, and selenium powder were weighed and mixed in a quartz tube with a molar ratio of 1:1:3, and 2.5 mg / mL iodine particles were added; the vacuum was evacuated to ≤1 Pa, and then the quartz tube containing the sample was sealed using a flame sealing device.

[0053] Step 2: Dual-temperature zone high temperature firing

[0054] Place the already vacuum-sealed quartz tube horizontally in a two-temperature-zone tube furnace. The raw materials are concentrated at the sealed end of the quartz tube, and this end is placed at the thermocouple of the high-temperature zone of the two-temperature-zone tube furnace, while the pointed end of the quartz tube is placed at the thermocouple of the low-temperature zone. The temperature of the low-temperature zone is controlled at 900 °C, and the temperature of the high-temperature zone is controlled at 1000 °C. It is heated from room temperature to the specified temperature in 390 min and held at this temperature gradient for 5 days. Subsequently, the vacuum-sealed quartz tube is naturally cooled to room temperature. Place the grown material in alcohol, wash and dry it.

[0055] Analyze and characterize the morphology, structure, and chemical composition of the material obtained in Comparative Example 3 by an optical microscope, an X-ray diffractometer, and a scanning electron microscope to determine that the material obtained under this condition has a chemical composition of VCrSe3, and its crystal structure can be indexed by I2 / m the structure. However, by comparing with Example 1, it is found that the single crystal size obtained under this experimental condition is smaller (as Figure 9 shown). This indicates that the addition concentration of iodine will affect the size of the single crystal.

[0056] In summary, the ternary magnetic selenide with the chemical formula VCrSe3 prepared by the present invention is a large-size and high-quality single crystal, and its crystal structure is monoclinic ( I 2 / m ). It is an intrinsically magnetically ordered transition metal chalcogenide crystal and has a definite molecular structural formula and stoichiometric ratio. Therefore, the properties of the compound are stable. In addition, through the study of the magnetotransport properties of this selenide, it is found that this selenide has magnetism at low temperatures and has application potential in the fields of spintronics, optoelectronics, etc.

[0057] It can be understood that for those of ordinary skill in the art, equivalent substitutions or changes can be made according to the technical solutions and inventive concepts of the present invention, and all such changes or substitutions should fall within the protection scope of the claims appended to the present invention.

Claims

1. A ternary magnetic selenide single crystal, characterized in that, The chemical formula of the selenide is VCrSe3, and its crystal structure is monoclinic I2 / m.

2. A method for preparing a ternary magnetic selenide single crystal, characterized in that, The ternary magnetic selenide is the ternary magnetic selenide described in Claim 1; the method uses vanadium powder, chromium powder, and selenium powder with a molar ratio of 1:1:3 as raw materials, uses iodine particles as a transport agent, and obtains a single crystal of ternary magnetic selenide through high-temperature firing and transport growth in a two-temperature zone: The method specifically includes the following steps: Take vanadium powder, chromium powder, selenium powder, and iodine particles, mix them evenly, enclose them in a quartz tube, and make the vacuum degree in the quartz tube ≤ 1 Pa. Place the end of the quartz tube with materials in the high-temperature zone of the two-temperature furnace, and the end without materials in the low-temperature zone of the two-temperature furnace; heat up, make the temperature at the low-temperature zone end be 900 ± 25 °C, and the temperature at the high-temperature zone end be 1000 ± 25 °C. Keep the temperature for 5 to 10 days under this temperature condition, then cool to room temperature, and after cleaning and drying, obtain a single crystal of ternary magnetic selenide.

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