аналитика - Condensed Matter Physics - # Anisotropic Planar Hall Effect in Topological Insulator-Ferromagnet Heterostructures

Anisotropic Planar Hall Effect in Bi2Se3/EuS Interfaces: Interplay of Proximity-Induced Spin Canting and Topological Spin Texture

Q: How would the planar Hall effect be affected by varying the thickness of the EuS layer and the interface quality between Bi2Se3 and EuS?

The thickness of the EuS layer plays a crucial role in determining the magnetic properties and the resultant planar Hall effect (PHE) at the Bi2Se3/EuS interface. As the thickness of the EuS layer increases, the proximity effect enhances the Curie temperature (Tc) of the EuS, leading to stronger ferromagnetic ordering. This enhancement can result in a more pronounced canting of the Eu moments, which directly influences the anisotropic planar Hall conductivity. A thicker EuS layer may also lead to a transition from out-of-plane to in-plane magnetic anisotropy, altering the symmetry and periodicity of the PHE. Moreover, the quality of the interface between Bi2Se3 and EuS is critical. A high-quality interface with minimal defects and impurities will facilitate better proximity coupling, enhancing the spin-orbit coupling effects and the Berry curvature contributions to the PHE. Conversely, a poor interface quality can introduce scattering mechanisms that diminish the PHE, leading to a less distinct Hall signal. Therefore, both the thickness of the EuS layer and the interface quality are vital parameters that can significantly modulate the characteristics of the anisotropic planar Hall effect.

Q: Can the anisotropic planar Hall effect be utilized to detect the presence and orientation of magnetic skyrmions at the Bi2Se3/EuS interface?

Yes, the anisotropic planar Hall effect can be effectively utilized to detect the presence and orientation of magnetic skyrmions at the Bi2Se3/EuS interface. The presence of skyrmions, which are topologically non-trivial spin textures, can lead to unique signatures in the planar Hall conductivity due to their associated scalar spin chirality. When skyrmions are present, they can interact with the gapped Dirac surface states of Bi2Se3, resulting in a topological Hall effect that manifests as a distinct contribution to the planar Hall conductivity. The orientation of skyrmions can also influence the PHE, as the deformation of skyrmions under an applied magnetic field can lead to changes in the Berry curvature and, consequently, the Hall response. By analyzing the angular dependence and the magnitude of the planar Hall conductivity, one can infer the presence of skyrmions and their orientation. This capability makes the anisotropic planar Hall effect a powerful tool for probing complex magnetic textures at the interface, providing insights into the underlying magnetic interactions and dynamics.

Q: What other types of magnetic textures, beyond skyrmions, could emerge at the Bi2Se3/EuS interface and how would they influence the planar Hall response?

Beyond skyrmions, several other types of magnetic textures could emerge at the Bi2Se3/EuS interface, including magnetic vortices, domain walls, and hedgehogs. Each of these textures can significantly influence the planar Hall response due to their unique spin configurations and associated topological properties. Magnetic Vortices: These are localized spin structures that can form in thin magnetic films. The presence of magnetic vortices can lead to a non-trivial contribution to the planar Hall effect, as the in-plane rotation of spins can create a complex Berry curvature landscape. This can result in a distinct angular dependence in the Hall conductivity, similar to that observed with skyrmions. Domain Walls: The presence of domain walls, which separate regions of different magnetization directions, can also affect the planar Hall response. The movement and dynamics of domain walls under an applied magnetic field can lead to changes in the local Berry curvature, resulting in a measurable Hall signal. The interaction between domain walls and the topological surface states of Bi2Se3 can provide insights into the magnetic domain structure and its evolution. Hedgehogs: These are another type of topological spin texture characterized by a radial arrangement of spins. Hedgehogs can also contribute to the planar Hall effect through their unique spin configurations, which can lead to a non-zero scalar spin chirality. The detection of hedgehogs via the planar Hall effect would provide valuable information about the magnetic interactions at the interface. In summary, the emergence of various magnetic textures at the Bi2Se3/EuS interface can lead to rich and complex behaviors in the planar Hall response, making it a versatile tool for studying magnetic phenomena in topological insulator systems.

Основные понятия

The planar Hall conductivity in Bi2Se3/EuS interfaces exhibits distinct anisotropic features depending on the orientation and magnitude of the proximity-induced magnetic moment in EuS, as well as the presence of a topological spin texture such as magnetic skyrmions.

Аннотация

The paper investigates the electronic transport properties, particularly the planar Hall effect, in Bi2Se3/EuS heterostructures. The authors use a realistic model Hamiltonian and a semi-classical Boltzmann transport formalism to analyze the system.

Key highlights:

The proximity coupling between the topological insulator Bi2Se3 and the ferromagnetic insulator EuS can lead to a canting of the Eu magnetic moments, which in turn modifies the electronic structure of the Bi2Se3 surface states.
The anisotropy in the planar Hall conductivity arises from the asymmetric Berry curvature of the gapped topological surface states, which depends on the orientation and magnitude of the proximity-induced Eu magnetic moment.
For a fixed Eu moment orientation, the planar Hall conductivity can exhibit symmetric, antisymmetric or anisotropic behavior with respect to the in-plane magnetic field angle, depending on the canting angles.
When the Eu moment is free to reorient with the applied in-plane field, the planar Hall conductivity is dominant in a specific range of field values, determined by the critical fields.
The authors also explore the possibility of a topological Hall effect arising from magnetic skyrmions that can form at the Bi2Se3/EuS interface due to the interplay of ferromagnetic exchange, Dzyaloshinskii-Moriya interaction, and the perpendicular alignment of the Eu moment.

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Статистика

The Eu magnetic moment m is varied from 0 to 6.9 μB.
The critical in-plane magnetic field values Bc' and Bc are in the range of 10-30 mT.
The initial polar canting angle θm0 of the Eu moment is varied from 0° to 45°.

Цитаты

"The anisotropy in the planar Hall conductivity arises from the asymmetric Berry curvature of the gapped topological surface states."
"The PHC is dominant for the in-plane field in the second regime, |Bc'| ≤ |Bin| ≤ |Bc|."
"Magnetic skyrmions can appear naturally when the Eu moment is aligned out of the interface plane, as found in the first-principle analysis of the interface."

Ключевые выводы из

Anisotropic planar Hall effects in Bi$_2$Se$_3$/EuS interfaces: Deciphering the role of proximity induced spin canting and topological spin texture

by Juhi Singh, ... в arxiv.org 10-03-2024

https://arxiv.org/pdf/2403.04533.pdf

Anisotropic planar Hall effects in Bi$_2$Se$_3$/EuS interfaces: Deciphering the role of proximity induced spin canting and topological spin texture

Дополнительные вопросы

How would the planar Hall effect be affected by varying the thickness of the EuS layer and the interface quality between Bi2Se3 and EuS?

The thickness of the EuS layer plays a crucial role in determining the magnetic properties and the resultant planar Hall effect (PHE) at the Bi2Se3/EuS interface. As the thickness of the EuS layer increases, the proximity effect enhances the Curie temperature (Tc) of the EuS, leading to stronger ferromagnetic ordering. This enhancement can result in a more pronounced canting of the Eu moments, which directly influences the anisotropic planar Hall conductivity. A thicker EuS layer may also lead to a transition from out-of-plane to in-plane magnetic anisotropy, altering the symmetry and periodicity of the PHE.
Moreover, the quality of the interface between Bi2Se3 and EuS is critical. A high-quality interface with minimal defects and impurities will facilitate better proximity coupling, enhancing the spin-orbit coupling effects and the Berry curvature contributions to the PHE. Conversely, a poor interface quality can introduce scattering mechanisms that diminish the PHE, leading to a less distinct Hall signal. Therefore, both the thickness of the EuS layer and the interface quality are vital parameters that can significantly modulate the characteristics of the anisotropic planar Hall effect.

Can the anisotropic planar Hall effect be utilized to detect the presence and orientation of magnetic skyrmions at the Bi2Se3/EuS interface?

Yes, the anisotropic planar Hall effect can be effectively utilized to detect the presence and orientation of magnetic skyrmions at the Bi2Se3/EuS interface. The presence of skyrmions, which are topologically non-trivial spin textures, can lead to unique signatures in the planar Hall conductivity due to their associated scalar spin chirality. When skyrmions are present, they can interact with the gapped Dirac surface states of Bi2Se3, resulting in a topological Hall effect that manifests as a distinct contribution to the planar Hall conductivity.
The orientation of skyrmions can also influence the PHE, as the deformation of skyrmions under an applied magnetic field can lead to changes in the Berry curvature and, consequently, the Hall response. By analyzing the angular dependence and the magnitude of the planar Hall conductivity, one can infer the presence of skyrmions and their orientation. This capability makes the anisotropic planar Hall effect a powerful tool for probing complex magnetic textures at the interface, providing insights into the underlying magnetic interactions and dynamics.

What other types of magnetic textures, beyond skyrmions, could emerge at the Bi2Se3/EuS interface and how would they influence the planar Hall response?

Beyond skyrmions, several other types of magnetic textures could emerge at the Bi2Se3/EuS interface, including magnetic vortices, domain walls, and hedgehogs. Each of these textures can significantly influence the planar Hall response due to their unique spin configurations and associated topological properties.

Magnetic Vortices: These are localized spin structures that can form in thin magnetic films. The presence of magnetic vortices can lead to a non-trivial contribution to the planar Hall effect, as the in-plane rotation of spins can create a complex Berry curvature landscape. This can result in a distinct angular dependence in the Hall conductivity, similar to that observed with skyrmions.

Domain Walls: The presence of domain walls, which separate regions of different magnetization directions, can also affect the planar Hall response. The movement and dynamics of domain walls under an applied magnetic field can lead to changes in the local Berry curvature, resulting in a measurable Hall signal. The interaction between domain walls and the topological surface states of Bi2Se3 can provide insights into the magnetic domain structure and its evolution.

Hedgehogs: These are another type of topological spin texture characterized by a radial arrangement of spins. Hedgehogs can also contribute to the planar Hall effect through their unique spin configurations, which can lead to a non-zero scalar spin chirality. The detection of hedgehogs via the planar Hall effect would provide valuable information about the magnetic interactions at the interface.

In summary, the emergence of various magnetic textures at the Bi2Se3/EuS interface can lead to rich and complex behaviors in the planar Hall response, making it a versatile tool for studying magnetic phenomena in topological insulator systems.