Ternary magnetic selenide and preparation method of single crystal of ternary magnetic selenide

Abstract

The invention discloses a ternary magnetic selenide and a preparation method of a single crystal of the ternary magnetic selenide, and relates to the technical field of crystal material preparation. The chemical formula of the ternary magnetic selenide is VCrSe3, and the ternary magnetic selenide can be prepared by taking a vanadium source, a chromium source and a selenium source in a specific proportion as raw materials and an iodine source as a transport agent through a chemical vapor transport method. The crystal structure of the VCrSe3 single crystal is a monoclinic phase (I2 / m), and phase transformation from antiferromagnetic to ferromagnetic and spin reorientation occur at low temperature, so that the VCrSe3 single crystal has application potential in the fields of spintronics, optoelectronics and the like; the large-size and high-quality VCrSe3 single crystal prepared by the method can provide a material for intrinsic physical property research and development of functional devices such as optoelectronic devices and spinning electrons.

Description

Technical Field

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

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

[0003] At present, 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 introduce magnetic transition metal sulfide compounds by element intercalation or doping. Among them, for chromium-based magnetic selenides, the Chinese invention patent with publication number CN 118653214 B discloses "a method for preparing vanadium-doped layered selenides and single crystals thereof", and specifically discloses regulating the electrical transport properties of Cr2Se3 by vanadium doping. However, the resistance-temperature variation curve does not show the characteristics of the material's magnetic phase transition, 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 in actual preparation, and it is easy to introduce point defects and other problems; at the same time, the performance of the material is affected by the element doping content, which is not conducive to obtaining materials with stable electromagnetic properties.

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

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for preparing a ternary magnetic selenide and a single crystal thereof, aiming to solve the problem of vanadium-doped selenide V in the prior art. x Cr 2-x Se3 (0<x≤0.25) has the defect of insufficient magnetic transport performance at low temperature.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A ternary magnetic selenide, wherein the chemical formula of the selenide is VCrSe3 and its crystal structure is monoclinic I 2 / m .

[0007] 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 in a molar ratio of 1:1:3 as raw materials, iodine particles as a transport agent, and obtains a ternary magnetic selenide single crystal through high-temperature sintering and transport growth in a dual-temperature zone.

[0008] The preparation method of the ternary magnetic selenide single crystal comprises the following steps: taking vanadium powder, chromium powder, selenium powder and iodine particles, mixing them, sealing them in a quartz tube, and making the vacuum degree in the quartz tube ≤1Pa, placing the end of the quartz tube with the material in the high temperature zone of a dual-temperature furnace, and placing the end without the material in the low temperature zone of the dual-temperature furnace; heating the tube so that the temperature of the low temperature zone end is 900±25°C and the temperature of the high temperature zone end is 1000±25°C, keeping the temperature under this temperature condition for 5 to 10 days, cooling to room temperature, and obtaining the ternary magnetic selenide single crystal after cleaning and drying.

[0009] Beneficial effects: The present invention provides a ternary magnetic selenide, whose chemical formula is VCrSe3 and whose crystal structure is monoclinic phase. I 2 / m It is a transition metal sulfide compound crystal with intrinsic magnetic order and a definite molecular structure and stoichiometric ratio, so the performance of the compound is stable. In addition, through the study of the magnetic transport properties of the selenide, it was found that the selenide is magnetic at low temperatures, so it has application potential in the fields of spin electronics and optoelectronics.

[0010] The second aspect of the present invention also provides a method for preparing a ternary magnetic selenide single crystal. By using a specific raw material molar ratio and a dual-temperature zone growth environment, the controllable synthesis of large-size, high-quality ternary magnetic selenide VCrSe3 single crystals is achieved, providing materials for the physical property research of such materials and the production of functional devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is an optical photograph of the VCrSe3 single crystal in Example 1.

[0012] Figure 2 This is the X-ray diffraction analysis spectrum of the VCrSe3 single crystal in Example 1.

[0013] Figure 3 This is the X-ray diffraction analysis spectrum of the VCrSe3 powder in Example 1.

[0014] Figure 4 This is the surface morphology of the VCrSe3 single crystal in Example 1.

[0015] Figure 5This is the energy spectrum of the VCrSe3 single crystal in Example 1.

[0016] Figure 6 This is the atomic resolution structure diagram of the VCrSe3 single crystal in Example 1 in the

[010] projection direction.

[0017] Figure 7 The curve of the magnetic susceptibility of the VCrSe3 sample in Example 1 at 500 Oe versus temperature (zero field cooling ZFC, external magnetic field B = 500 Oe) and the first derivative of magnetization with temperature.

[0018] Figure 8 This is a curve chart showing the change of magnetization intensity of the VCrSe3 sample in Example 1 with the magnetic field at different temperatures.

[0019] Fig. 9 This is an optical photograph of the VCrSe3 single crystal in Comparative Example 3. DETAILED DESCRIPTION

[0020] The present invention provides a method for preparing a ternary magnetic selenide and a single crystal thereof. To make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the following examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] In the prior art, due to the vanadium-doped layered V x Cr 2-x Although Se3 (0<x≤0.25) can regulate the electrical transport properties of the material, its doping concentration is a variable, and the material's performance is affected by the element doping content, so it is not conducive to obtaining materials with stable electromagnetic properties, and doping does not significantly change the material's antiferromagnetic magnetic properties at low temperatures.

[0022] In view of the above problems, the present invention discloses a ternary magnetic selenide, the chemical formula of which is VCrSe3, and the crystal structure of which is a monoclinic phase ( I 2 / m ), is a transition metal sulfide crystal with intrinsic magnetic order, and the compound has a definite molecular structure and stoichiometric ratio, so the performance of the compound is stable. Through the study of the magnetic transport properties of the selenide, it was found that within the test temperature range of 2 to 300K (such as Figure 7As shown in the figure, the selenide undergoes two magnetic property transitions at low temperatures. In the temperature range from room temperature to 35 K, the selenide exhibits antiferromagnetic properties; as the temperature drops to about 35 K, its antiferromagnetic phase transforms into a ferrimagnetic phase; when the temperature continues to drop to about 10 K, spin reorientation occurs in the selenide. It can be seen that the selenide has an obvious hysteresis loop at low temperatures and exhibits high-field unsaturation, indicating that the selenide is magnetic at low temperatures. Therefore, this magnetically ordered atomic crystal can provide a basis for studying the single crystal magnetic ground state, fundamental excitations, and magnon dynamics, and has application potential in the fields of spin electronics and optoelectronics.

[0023] The second aspect of the present invention also provides a method for preparing the ternary magnetic selenide single crystal, wherein the method uses vanadium powder, chromium powder, and selenium powder in a molar ratio of 1:1:3 as raw materials, and iodine particles as a transport agent, and obtains the ternary magnetic selenide single crystal as described above by high-temperature firing and transport growth in a dual-temperature zone. The preparation method has simple steps and is easy to implement. It can be achieved by using a gas phase transport method in a furnace with a dual-temperature zone with raw materials of a specific ratio, and the prepared crystal is a large-size, high-quality single crystal, which provides materials for subsequent research on the ternary magnetic selenide.

[0024] In the preparation method, the mass purity of the vanadium powder, chromium powder, selenium powder and iodine particles is ≥99.99% to reduce the influence of impurities on crystal formation; at the same time, the added concentration of iodine particles is controlled to be 10 mg / mL to have better transport performance and make subsequent cleaning of the crystals easier.

[0025] As an optimization scheme, the preparation method of the ternary magnetic selenide single crystal specifically includes the following steps: taking vanadium powder, chromium powder and selenium powder in a molar ratio of 1:1:3, mixing and placing in a quartz tube, adding 10 mg / mL of iodine particles, evacuating and making the vacuum degree in the quartz tube ≤1Pa, and sealing the quartz tube; placing the end of the quartz tube with material in the high temperature zone of a dual-temperature furnace, and placing the end without material in the low temperature zone of the dual-temperature furnace; heating to make the temperature of the low temperature zone end 900±25°C, and the temperature of the high temperature zone end 1000±25°C, keeping warm at this temperature gradient for 5 to 10 days, cooling to room temperature, and obtaining a ternary magnetic selenide single crystal after cleaning and drying.

[0026] The ternary magnetic selenide single crystal prepared by this method is as follows: Figure 1 As shown, it has a large size and can provide materials for the study of its physical and chemical properties.

[0027] To further illustrate a ternary magnetic selenide single crystal and a preparation method thereof provided by the present invention, the following examples are provided.

[0028] Example 1 A method for preparing a ternary magnetic selenide single crystal comprises the following steps: Step 1: Ingredients and packaging 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.

[0029] Step 2: Dual-temperature zone high temperature firing 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.

[0030] 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 6The 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 the material, it can be determined that the material obtained by the preparation method is a single crystal, its growth orientation is (00l) direction, the chemical composition is VCrSe3, and the microscopic morphology shows a distinct striped orientation structure. Combined with X-ray diffraction and electron microscope microscopic analysis, it can be determined that the crystal structure of VCrSe3 is monoclinic ( I2 / m ).

[0031] In addition, the magnetic transport properties of the obtained material were characterized by superconducting quantum interference. The magnetization intensity of the material sample was measured as a function of temperature (zero field cooling ZFC, external magnetic field B = 500 Oe), and the first-order derivative of the magnetization intensity and temperature was plotted. The results are shown in Figure 7 As shown. Figure 7 It can be seen that within the test temperature range of 2 to 300 K, the sample undergoes two magnetic property transitions at low temperatures. From room temperature to 35 K, the sample exhibits antiferromagnetic properties; as the temperature drops to around 35 K, the antiferromagnetic phase transitions to the ferrimagnetic phase; when the temperature continues to drop to around 10 K, spin reorientation occurs in the sample. In addition, the changes in the magnetization intensity of VCrSe3 at different temperatures with the magnetic field intensity were also measured. Figure 8 As shown. Figure 8 It can be seen that VCrSe3 has an obvious hysteresis loop at low temperature and exhibits high-field unsaturation phenomenon, indicating that the sample is magnetic at low temperature.

[0032] Example 2 Step 1: Ingredients and packaging 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.

[0033] Step 2: Dual-temperature zone high temperature firing 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.

[0034] 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 ).

[0035] Comparative Example 1 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.

[0036] 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.

[0037] Comparative Example 2 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.

[0038] 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.

[0039] Comparative Example 3 Step 1: Ingredients and packaging 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.

[0040] Step 2: Dual-temperature zone high temperature firing Place the vacuum-sealed quartz tube flat in a dual-zone tubular furnace. The raw materials are concentrated at one end of the quartz tube, which is placed at the thermocouple at the high-temperature end of the dual-zone tubular furnace. The tip of the quartz tube is placed at the thermocouple at the low-temperature end. The temperature at the low-temperature end is controlled at 900 °C, and the temperature at the high-temperature end is controlled at 1000 °C. The temperature is raised from room temperature to the specified temperature over 390 min, and the temperature is kept at this temperature gradient for 5 days. Subsequently, the vacuum-sealed quartz tube is naturally cooled to room temperature. The grown material is placed in alcohol, cleaned and dried.

[0041] The morphology, structure and chemical composition of the material obtained in Comparative Example 3 were analyzed and characterized by optical microscopy, X-ray diffractometer and scanning electron microscopy, and it was determined that the chemical composition of the material obtained under this condition was VCrSe3, and the crystal structure could be I2 / m However, by comparing with Example 1, it is found that the size of the single crystal obtained under this experimental condition is smaller (e.g. Fig. 9 This indicates that the concentration of iodine addition affects the size of the single crystal.

[0042] In summary, the ternary magnetic selenide with the chemical formula VCrSe3 prepared by the present invention is a large-sized, high-quality single crystal, and its crystal structure is a monoclinic phase ( I 2 / m ), is a transition metal sulfide compound crystal with intrinsic magnetic order and a definite molecular structure and stoichiometric ratio, so the performance of the compound is stable. In addition, through the study of the magnetic transport properties of the selenide, it was found that the selenide is magnetic at low temperatures and has application potential in the fields of spin electronics and optoelectronics.

[0043] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of the present invention, and all these changes or substitutions should fall within the protection scope of the claims attached to the present invention.

Claims

1. A ternary magnetic selenide, characterized in that: The chemical formula of the selenide is VCrSe3, and its crystal structure is monoclinic I 2 / m .

2. A method for preparing a ternary magnetic selenide single crystal, characterized in that: The ternary magnetic selenide is the ternary magnetic selenide as claimed in claim 1; the method uses vanadium powder, chromium powder and selenium powder with a molar ratio of 1:1:3 as raw materials, iodine particles as a transport agent, and obtains a ternary magnetic selenide single crystal through high-temperature sintering and transport growth in a dual-temperature zone.

3. The method for preparing a ternary magnetic selenide single crystal according to claim 2, characterized in that: The method comprises the following steps: taking vanadium powder, chromium powder, selenium powder and iodine particles, mixing them evenly, sealing them in a quartz tube, making the vacuum degree in the quartz tube ≤1Pa, placing one end of the quartz tube with materials in a high temperature zone of a dual-temperature furnace, and placing the other end without materials in a low temperature zone of the dual-temperature furnace; raising the temperature to make the temperature of the low temperature zone end 900±25°C and the temperature of the high temperature zone end 1000±25°C, keeping the temperature under the temperature condition for 5 to 10 days, cooling to room temperature, and obtaining a ternary magnetic selenide single crystal after cleaning and drying.

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