Antiferromagnetic single crystals of zero-field in-plane anomalous hall effect, methods of making, applications

Abstract

The application discloses a kind of zero-field in-plane anomalous Hall effect of antiferromagnetic single crystal, preparation method and application, belong to the field of condensed matter physics.The technical points are as follows: the chemical general formula of the antiferromagnetic single crystal is Mn5Si3;Mn5Si3 Single crystal is hexagonal system at room temperature and belongs to P63 / mcm space group, and space group number is 193;It is orthorhombic at 100K-60K, belongs to Cmcm space group, and space group number is 63;It is monoclinic system below 60K, belongs to P21 / m space group, and space group number is 11.The single crystal alloy proposed in the application can realize zero-field in-plane anomalous Hall effect at low temperature, and has the characteristics of strong anti-external magnetic field interference ability, no stray field, etc., and is a candidate material for magnetic storage and magnetic detector research and development.

Description

Technical Field

[0001] This invention relates to the technical field of condensed matter physics, and more specifically, to an antiferromagnetic single crystal exhibiting an anomalous Hall effect in a zero-field region, its preparation method, and its applications. Background Technology

[0002] The anomalous Hall effect is an important electrical transport property in spintronics. It refers to the physical phenomenon where, when an electric current passes through a magnetic conductor, a charge accumulates transversely perpendicular to the current direction, thus forming a transverse voltage (e.g., Z. Fang, N. Nagaosa, KS Takahashi, A. Asamitsu, R. Mathieu, T. Ogasawara, H. Yamada, M. Kawasaki, Y. Tokura, and K. Terakura, The Anomalous Hall Effect and Magnetic Monopoles in Momentum Space, Science 302, 92 (2003)). This effect has wide applications in signal detection and information storage devices. For example, in nanoscale devices, due to the limitations of conventional magnetic measurement methods, the anomalous Hall effect has become an important measurement tool due to its excellent sensitivity and superior integration convenience.

[0003] However, the anomalous Hall effect also has a significant limitation—it can only detect out-of-plane magnetization. This inherent characteristic greatly restricts its application range, especially in ferromagnetic materials, where in-plane magnetization is usually observed. Therefore, in practical applications, detecting in-plane magnetization often requires more complex device architectures or indirect measurement methods.

[0004] Previous theoretical studies have shown that the anomalous Hall effect also occurs when the applied magnetic field is along the in-plane direction (e.g., J. Zhou et al., Heterodimensional superlattice with in-plane anomalous Hall effect, Nature 609, 46 (2022)). To distinguish between these two different types of anomalous Hall effects, the anomalous Hall effect generated along an out-of-plane magnetic field is usually called the "out-of-plane anomalous Hall effect (OPAHE)," while the one generated along an in-plane magnetic field is called the "in-plane anomalous Hall effect (IPAHE)." The emergence of the in-plane anomalous Hall effect breaks through the limitation of the out-of-plane anomalous Hall effect, which can only detect out-of-plane magnetization, and provides a simplified scheme for the direct measurement of in-plane magnetization.

[0005] In recent years, the in-plane anomalous Hall effect has been proven to exist in paramagnetic, ferromagnetic, and some antiferromagnetic materials with low symmetry, strong anisotropy, and broken mirror rotational symmetry. Currently, most materials exhibiting the in-plane anomalous Hall effect show a linear relationship between the effect and the magnetic field, i.e., they are magnetic field dependent. Therefore, both out-of-plane and in-plane anomalous Hall effect materials have their limitations, making it difficult to meet the current application requirements of signal detection and information storage devices. Thus, antiferromagnetic materials with a zero-plane in-plane anomalous Hall effect not only possess advantages such as high spin dynamic response frequency, low stray field, and resistance to external field interference, but also have broad application prospects in signal detection and information storage devices.

[0006] In summary, there is an urgent need to develop a novel in-plane anomalous Hall effect material with antiferromagnetic magnetism, zero-plane in-plane anomalous Hall effect, low cost, and simple fabrication process. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing an antiferromagnetic single crystal exhibiting an in-zero field anomalous Hall effect. Another objective of this invention is to provide a method for preparing an antiferromagnetic single crystal exhibiting an in-zero field anomalous Hall effect.

[0008] Another object of the present invention is to provide an application of an antiferromagnetic single crystal with an anomalous Hall effect in a zero field.

[0009] The technical solution of this invention is: An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field has the general chemical formula Mn5Si3. At room temperature, the Mn5Si3 single crystal is hexagonal and belongs to space group P63 / mcm (space group number 193). Between 100K and 60K, it is orthorhombic and belongs to space group Cmcm (space group number 63). Below 60K, it is monoclinic and belongs to space group P21 / m (space group number 11).

[0010] An antiferromagnetic single crystal exhibiting an in-plane anomalous Hall effect is characterized by having the general chemical formula Mn5Si3. The Mn5Si3 material is in a non-coplanar antiferromagnetic state below 60 K, with a lattice distortion of monoclinic structure. The Mn atoms are arranged in a non-coplanar antiferromagnetic array, disrupting the system's mirror symmetry and rotational symmetry, leading to spin splitting of the material's band structure. Simultaneously, due to trigonometric frustration, the material generates a small net magnetic moment of 0.04 μB / fu along the c-axis. This small net magnetic moment disrupts the system's time-reversal joint symmetry and, together with the disrupted spatial symmetry, satisfies the symmetry conditions for generating the in-plane anomalous Hall effect.

[0011] Furthermore, the magnetic transition temperature of Mn5Si3 single crystal is T. N1 =100 K, T N2 =60 K; where, T N1 T represents the temperature at which the paramagnetic state transitions to the collinear antiferromagnetic state. N2 This represents the temperature at which the antiferromagnetic state transitions from a collinear antiferromagnetic state to a non-coplanar antiferromagnetic state. Furthermore, the paramagnetic transition temperature of Mn5Si3 single crystal is T. N =100K and Mn5Si3 single crystal is a hexagonal prism with a metallic luster at room temperature, with hexagonal side lengths greater than 0.5mm and a thickness greater than 3mm.

[0012] Furthermore, at room temperature, the lattice constants of Mn5Si3 single crystal are: a=b=6.9110 Å, c=4.8166 Å, α=β=90°, γ=120°; Where a represents the lattice constant of the bottom surface of the unit cell along the a-axis, b represents the lattice constant of the bottom surface of the unit cell along the b-axis, and c represents the lattice constant of the unit cell along the c-axis; α represents the crystal axis angle between the a-axis and the c-axis, β represents the crystal axis angle between the b-axis and the c-axis, and γ represents the crystal axis angle between the a-axis and the b-axis.

[0013] Furthermore, the in-plane anomalous Hall conductivity of Mn5Si3 single crystal is as follows: when the magnetic field is along the z-direction, the maximum value is 3 S / cm in the zx plane and 10 S / cm in the yz plane.

[0014] Furthermore, the temperature range of the zero-field anomalous Hall effect of the antiferromagnetic single crystal is [2 K, 60 K].

[0015] A method for preparing an antiferromagnetic single crystal exhibiting anomalous Hall effect in a zero-field environment includes the following steps: S100, with Cu as flux, three metal raw materials Mn:Si:Cu are mixed in a molar ratio of 15:9:26 and loaded into a crucible (Cu is a flux used to lower the melting point of Mn and Si and provide a solution environment for material growth). S200, the crucible is vacuum-sealed in a quartz tube; S300 is used to sinter quartz tubes for single crystal growth in a pit furnace. The growth temperature program of the pit furnace is as follows: the temperature is increased from room temperature to 1150℃ at a rate of 112℃ / h, held for 24h, then decreased to 1000℃ at a rate of 50℃ / h, then increased to 1050℃ at a rate of 50℃ / h, and then decreased to 850℃ at a rate of 1.5℃ / h. Finally, the flux is separated by centrifugation to obtain antiferromagnetic Mn5Si3 single crystal.

[0016] Application of an antiferromagnetic single crystal with anomalous Hall effect in zero field in magnetic storage or magnetic detection.

[0017] An application of an antiferromagnetic single crystal with zero-field in-situ anomalous Hall effect in magnetic storage, which enables direct electrical readout of in-situ magnetization information.

[0018] An application of an antiferromagnetic single crystal with zero-plane in-plane anomalous Hall effect in magnetic detection, which can directly detect in-plane magnetic states.

[0019] The beneficial effects of this application are as follows: First, this invention provides an antiferromagnetic single crystal Mn5Si3 exhibiting an in-plane anomalous Hall effect at zero field. This single crystal can generate an in-plane anomalous Hall effect in a low-temperature antiferromagnetic phase at zero field without the need for an external magnetic field. Specifically, at temperatures below 60 K, the material is in a non-coplanar antiferromagnetic state and possesses a small net magnetic moment (0.04 μB / fu) along the c-axis of the crystal, thereby enabling an in-plane anomalous Hall response under zero field conditions.

[0020] Secondly, this invention also provides a method for preparing antiferromagnetic Mn5Si3 single crystals using a flux method. This method has a clear process flow, is simple to operate, and has low cost, effectively obtaining the target single crystal material. The Mn5Si3 single crystals prepared using this method exhibit excellent antiferromagnetic properties and generate almost no stray fields, providing a material basis for the realization and application of its anomalous Hall effect in the zero-field region.

[0021] Third, based on the above-mentioned zero-plane in-plane anomalous Hall effect, this invention realizes the direct electrical readout of in-plane magnetization information, breaking through the limitation of the traditional anomalous Hall effect which is mainly sensitive to external magnetization and difficult to directly detect in-plane magnetization, thus providing a more direct and simplified technical solution for the detection of in-plane magnetic state.

[0022] Fourth, since the Mn5Si3 described in this invention is an antiferromagnetic single crystal and can generate an in-plane anomalous Hall response under zero external magnetic field conditions, it has the advantages of strong resistance to external field interference, small stray field, convenient signal reading and easy integration with micro and nano devices. It has good application prospects in the fields of high-density magnetic storage, high-sensitivity magnetic detection devices, novel spintronic devices and low-temperature magnetic sensing. Attached Figure Description

[0023] The present invention will be further described in detail below with reference to the embodiments shown in the accompanying drawings, but this does not constitute any limitation on the present invention.

[0024] Figure 1 This is a flowchart of the preparation of single-crystal Mn5Si3 according to the present invention.

[0025] Figure 2The relevant parameter diagrams for the Mn5Si3 single crystal of this invention are as follows: (a) is the XRD diffraction pattern of the Mn5Si3 single crystal powder and the Rietveld refinement results; (b) is the Mn5Si3 single crystal in ( h (c) is the XRD diffraction pattern of the plane, (d) is the energy dispersive X-ray spectrum of the Mn5Si3 single crystal, and the inset is a single crystal optical photograph.

[0026] Figure 3 The results are as follows: (a) Magnetocaloric curve of Mn5Si3 single crystal; (b) Magnetization curve of Mn5Si3 single crystal at different temperatures when the magnetic field is parallel to the z-direction; (c) Magnetization curve of Mn5Si3 single crystal at different temperatures when the magnetic field is perpendicular to the z-direction.

[0027] Figure 4 These are the measured resistivity results of out-of-plane Hall and in-plane anomalous Hall on the yz plane; (a) out-of-plane Hall effect, (b) in-plane anomalous Hall effect.

[0028] Figure 5 These are the measured results of out-of-plane Hall and in-plane anomalous Hall resistivity measurements on the zx plane; (a) out-of-plane Hall effect, (b) in-plane anomalous Hall effect.

[0029] Figure 6 This is the measured change in anomalous Hall conductivity with temperature within the zero field of the yz, zx plane.

[0030] Figure 7 This is a schematic diagram of the crystal and magnetic structures of the material Mn5Si3 of this invention under low-temperature operating conditions (AF1 phase, T<60K).

[0031] Figure 8 This refers to the spin splitting of the electronic bands of the material after the introduction of the net magnetic moment.

[0032] Figure 9 This is a schematic diagram showing the distribution of the Fermi level of the material in momentum space at the Berry curvature after the introduction of the net magnetic moment.

[0033] Figure 10 These are the theoretical calculation results of the materials of this invention. Detailed Implementation

[0034] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the materials used in the following embodiments are conventional materials; and the experimental methods described are conventional methods.

[0035] The present invention will now be described in detail with reference to the accompanying drawings, providing a complete description of the technical solution of the present invention.

[0036] <Example 1> <I. Preparation Method> like Figure 1 As shown, an antiferromagnetic single-crystal Mn5Si3 material exhibiting in-plane anomalous Hall effect is prepared by a flux method, comprising the following steps: S100, using Cu as flux, weigh Mn, Si and Cu metal raw materials in a molar ratio of 15:9:26 and mix them in a crucible, then vacuum seal the crucible in a quartz tube; S200, single crystal growth is carried out by sintering quartz tubes in a pit furnace. The growth temperature program of the pit furnace is as follows: heat up to 1150℃ at a rate of 112℃ / h, hold for 24h, then cool down to 1000℃ at a rate of 50℃ / h, then heat up to 1050℃ at a rate of 50℃ / h, and then cool down to 850℃ at a rate of 1.5℃ / h. S300, antiferromagnetic Mn5Si3 single crystal was obtained by centrifugation to separate the flux. Based on room temperature X-ray diffraction data, the sample can be determined to be a hexagonal crystal system (space group P63 / mcm), and the lateral face of the single crystal hexagonal prism is (100).

[0037] <II. Morphological, Structural and Compositional Characterization> The morphology, structure and composition of the Mn5Si3 single crystals prepared above were characterized.

[0038] like Figure 2 As shown in (a), the Mn5Si3 crystal prepared in this invention was tested by XRD diffraction, which showed that the Mn5Si3 single crystal had a hexagonal structure, belonged to the P63 / mcm space group, and had lattice constants a=b=6.9110Å, c=4.8166Å, α=β=90°, and γ=120°.

[0039] like Figure 2 As shown in (b), the Mn5Si3 crystal prepared by the present invention was tested on its (120) plane by an XRD diffractometer, which showed that the Mn5Si3 single crystal has a hexagonal structure, belongs to the P63 / mcm space group, and all diffraction peaks are

[100] orientation diffraction peaks with no impurity peaks, and correspond one-to-one with the standard card.

[0040] like Figure 2 As shown in (c), the Mn5Si3 crystal prepared by the present invention was analyzed by energy dispersive X-ray spectroscopy (EDS) elemental analysis, which showed that it was composed of two elements and had no impurity elements. Quantitative calculation showed that the ratio of the two elements was close to the stoichiometric ratio of 5:3. The preparation method of the present invention can obtain millimeter-sized hexagonal prism-shaped Mn5Si3 crystals, whose (001) crystal faces are hexagonal, with a side length greater than 0.5 mm and a thickness greater than 3 mm.

[0041] III. Magnetic Characterization Figure 3 (a) illustrates the magnetocaloric curves of Mn5Si3. From Figure 3 (a) It can be seen that the paramagnetic transition temperature T N =100 K.

[0042] Figure 3 (b) and Figure 3 (c) illustrates the magnetization curves of a Mn5Si3 single crystal at different temperatures with the magnetic field parallel and perpendicular to the z-direction. From Figure 3 (b) and Figure 3 (c) It can be seen that the magnetization intensity increases linearly with the magnetic field at low temperature, and a field-induced magnetization phase transition occurs under high field.

[0043] <IV. Out-of-plane and In-plane Anomalous Hall Effects> like Figure 4 As shown in (a), the out-of-plane Hall resistivity is at different temperatures in the yz plane. Figure 4 (b) shows the in-plane Hall resistivity of the yz plane at different temperatures.

[0044] like Figure 5 As shown in (a), the out-of-plane Hall resistivity of the zx plane at different temperatures is as follows: Figure 5 (b) shows the in-plane anomalous resistivity of the zx plane at different temperatures.

[0045] like Figure 6 As shown in (a), the out-of-field anomalous Hall conductivity in the yz plane zero plane varies with temperature, as follows: Figure 6 (b) shows the relationship between the out-of-field anomalous Hall conductivity of the zx plane and temperature.

[0046] <V. Mechanism Explanation> like Figure 7 As shown, the Mn5Si3 material is in a non-coplanar antiferromagnetic state below 60 K. At this temperature, the material's lattice distortion becomes a monoclinic structure, and the Mn atoms are arranged in a non-coplanar antiferromagnetic array, leading to the destruction of the system's mirror symmetry and rotational symmetry, thereby causing spin splitting of the material's band structure (see...). Figure 8 ).

[0047] Furthermore, due to trigonometric frustration, the material generates a small net magnetic moment of 0.04 μB / fu along the c-axis, i.e., the z-direction. This small net magnetic moment disrupts the time-reversal joint symmetry of the system and, together with the disrupted spatial symmetry, causes the material to satisfy the symmetry conditions for generating the in-plane anomalous Hall effect.

[0048] Under the above conditions, such as Figure 9As shown, the distribution of the Berry curvature of the electronic bands in momentum space no longer satisfies the symmetric cancellation relationship, thus resulting in a finite anomalous Hall conductivity after Brillouin zone integration. Therefore, the material can generate a zero-field in-plane anomalous Hall effect under zero external magnetic field conditions.

[0049] Furthermore, such as Figure 10 As shown, the calculation results indicate that when the small net magnetic moment is positive along the z-direction, the material exhibits a non-zero anomalous Hall conductivity; when the magnetic state reverses, the sign of the corresponding anomalous Hall conductivity is reversed. This shows that the anomalous Hall effect in the zero field originates from the synergistic effect of the material's own lattice structure, magnetic structure, and symmetry breaking, without the need for an external magnetic field or strain induction.

[0050] The above-described embodiments are preferred embodiments of the present invention and are only used to facilitate the illustration of the present invention. They are not intended to limit the present invention in any way. Any person skilled in the art who makes local modifications or alterations to the technical content disclosed in the present invention without departing from the scope of the technical features of the present invention shall still fall within the scope of the technical features of the present invention.

Claims

1. An antiferromagnetic single crystal exhibiting an in-zero field anomalous Hall effect, characterized in that, The general chemical formula of the antiferromagnetic single crystal is Mn5Si3; at room temperature, the Mn5Si3 single crystal is a hexagonal crystal system with space group P63 / mcm and space group number 193. At 100K-60K, Mn5Si3 single crystal is an orthorhombic crystal system with space group Cmcm and space group number 63. Below 60 K, Mn5Si3 single crystal is a monoclinic crystal system with space group P21 / m and space group number 11.

2. The antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1, characterized in that, The general chemical formula of the antiferromagnetic single crystal is Mn5Si3. The Mn5Si3 material is in a non-coplanar antiferromagnetic state below 60 K, and the material lattice is distorted into a monoclinic structure. The Mn atoms are arranged in a non-coplanar antiferromagnetic array, which leads to the destruction of the system's mirror symmetry and rotational symmetry, resulting in spin splitting of the material's band structure. At the same time, due to trigonometric frustration, the material generates a small net magnetic moment of 0.04 μB / fu along the c-axis. This small net magnetic moment destroys the system's time-reversal joint symmetry and, together with the already destroyed spatial symmetry, makes the material satisfy the symmetry conditions for generating the in-plane anomalous Hall effect.

3. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, The paramagnetic transition temperature of Mn5Si3 single crystal is 100K.

4. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, At room temperature, the lattice constants of Mn5Si3 single crystal are: a=b=6.9110Å, c=4.8166 Å, α=β=90°, γ=120°; where a and b represent the side lengths of the two equal-length edges on the bottom face of the unit cell, c represents the height of the unit cell, and α, β, and γ are all lattice angle parameters.

5. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, Mn5Si3 single crystal is a hexagonal prism with a metallic luster at room temperature. The hexagonal side length is greater than 0.5 mm and the thickness is greater than 3 mm.

6. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, The magnetic transition temperature of Mn5Si3 single crystal is T. N1 =100 K, T N2 =60 K; where, T N1 T represents the temperature at which the paramagnetic state transitions to the collinear antiferromagnetic state. N2 It represents the temperature at which the antiferromagnetic state transitions from a collinear antiferromagnetic state to a non-coplanar antiferromagnetic state.

7. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, The in-plane anomalous Hall conductivity of Mn5Si3 single crystal is 3 S / cm in the zx plane and 10 S / cm in the yz plane when the magnetic field is along the z direction.

8. An antiferromagnetic single crystal exhibiting anomalous Hall effect in zero field as described in claim 1 or 2, characterized in that, The temperature range of the anomalous Hall effect in the zero field is [2 K, 60 K].

9. A method for preparing an antiferromagnetic single crystal exhibiting anomalous Hall effect in a zero-field environment, characterized in that, Includes the following steps: S100, with Cu as flux, three metal raw materials Mn:Si:Cu in a molar ratio of 15:9:26 are mixed and loaded into a crucible; S200, the crucible is vacuum-sealed in a quartz tube; S300 is used to sinter quartz tubes for single crystal growth in a pit furnace. The growth temperature program of the pit furnace is as follows: the temperature is increased from room temperature to 1150℃ at a rate of 112℃ / h, held for 24h, then decreased to 1000℃ at a rate of 50℃ / h, then increased to 1050℃ at a rate of 50℃ / h, and then decreased to 850℃ at a rate of 1.5℃ / h. Finally, the flux is separated by centrifugation to obtain antiferromagnetic Mn5Si3 single crystal.

10. The application of the antiferromagnetic single crystal with zero-field anomalous Hall effect as described in any one of claims 1 to 9 in magnetic storage or magnetic detection.

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