Regulation of the Extrinsic Contribution to the Anomalous Hall Effect in Fe-rich Kagome Magnet Fe3Sn

Centrala begrepp

By increasing the iron content in the kagome magnet Fe3Sn, researchers successfully suppressed the extrinsic contribution to the anomalous Hall effect, leading to a dominant intrinsic contribution and a large anomalous Hall conductivity close to the theoretically predicted value.

Sammanfattning

Liu, M., Ma, L., Li, G., Zhen, C., Hou, D., & Zhao, D. (Year). Extrinsic suppression of anomalous Hall effect in Fe-rich kagome magnet Fe3Sn.

This study investigates the charge transport properties of Fe-rich Fe3Sn to understand how to suppress the extrinsic contribution to the anomalous Hall effect (AHE) and enhance the intrinsic contribution.

Viktiga insikter från

Extrinsic suppression of anomalous Hall effect in Fe-rich kagome magnet Fe3Sn

by Muhua Liu, L... på arxiv.org 11-04-2024

https://arxiv.org/pdf/2411.00746.pdf

Djupare frågor

How would the manipulation of other synthesis parameters, beyond Fe content, impact the observed AHE behavior in Fe3Sn?

Beyond simply tweaking the Fe content, several other synthesis parameters can significantly influence the observed Anomalous Hall Effect (AHE) behavior in Fe3Sn. Let's break down how these factors come into play:

Annealing Temperature and Duration: Annealing plays a critical role in determining the degree of atomic ordering within the crystal structure. Higher annealing temperatures and longer durations generally promote the diffusion of atoms, potentially leading to a more ordered structure with fewer defects. This enhanced ordering can reduce impurity scattering, thereby suppressing the extrinsic AHE contribution and bringing the intrinsic AHE, governed by the Berry phase, to the forefront.

Cooling Rate: The cooling rate after annealing dictates how quickly the atoms "freeze" into their positions. Rapid cooling, such as quenching, can trap defects and lead to a less ordered structure. This disorder can enhance impurity scattering, increasing the extrinsic AHE contribution. Conversely, slower cooling rates allow for greater atomic rearrangement, potentially leading to a more ordered structure and a more dominant intrinsic AHE.

Substrate Selection (for Thin Films): If Fe3Sn is grown as a thin film, the choice of substrate becomes crucial. Lattice mismatch between the substrate and the growing film can induce strain, which directly impacts the crystal structure and, consequently, the AHE. Strain can either enhance or suppress the AHE depending on its nature (tensile or compressive) and the specific material properties.

Doping with Other Elements: Intentionally introducing small amounts of other elements (beyond Fe and Sn) into the Fe3Sn lattice can modify its electronic structure and scattering behavior. Depending on the dopant's properties, it can either enhance or suppress the extrinsic or intrinsic AHE contributions.

Pressure: Applying pressure during synthesis can alter the lattice constants of Fe3Sn, effectively tuning its electronic band structure. This, in turn, can lead to changes in the Berry curvature and hence the intrinsic AHE.
In essence, optimizing these synthesis parameters is crucial for achieving the desired AHE behavior in Fe3Sn. By carefully controlling these factors, researchers can tailor the material's properties for specific spintronic applications.

Could the observed suppression of the extrinsic AHE in Fe-rich Fe3Sn be replicated in other topological materials with different crystal structures?

While the specific details of the AHE are material-dependent, the general principle of suppressing the extrinsic contribution by minimizing the spin-orbit coupling strength of impurity centers could potentially be extended to other topological materials. Here's why:

Universality of Extrinsic AHE Mechanisms: The extrinsic AHE arises from asymmetric scattering of charge carriers, primarily due to skew scattering and the side-jump mechanism. These mechanisms are not restricted to a particular crystal structure and are generally present in materials with impurities.

Spin-Orbit Coupling Dependence: The strength of skew scattering, a dominant extrinsic contribution, is directly related to the spin-orbit coupling strength of the scattering centers (impurities). This principle holds true regardless of the specific crystal structure.
Therefore, if a topological material exhibits a significant extrinsic AHE contribution due to skew scattering from impurities with strong spin-orbit coupling, replacing these impurities with atoms having weaker spin-orbit coupling could potentially suppress the extrinsic AHE.
However, the feasibility of this approach depends on several factors:

Solubility and Stability: The substitute atoms must be soluble in the host material and form a stable compound with the desired crystal structure.

Impact on Intrinsic Properties: The substitution should not significantly degrade the desired intrinsic topological properties of the material, such as the Berry curvature, which governs the intrinsic AHE.

Material-Specific Considerations: The effectiveness of this strategy will depend on the specific electronic band structure, the nature of the impurity states, and the dominant scattering mechanisms in the material.
In conclusion, while not universally guaranteed, the principle of manipulating impurity spin-orbit coupling to tune the extrinsic AHE holds promise for other topological materials. Careful material selection and synthesis control are essential for successful implementation.

What are the potential implications of controlling the anomalous Hall effect for the development of novel spintronic devices, particularly in the context of low-power consumption and high-speed data processing?

The ability to precisely control the anomalous Hall effect (AHE), particularly by enhancing the robust intrinsic contribution, opens up exciting possibilities for developing novel spintronic devices with desirable characteristics like low-power consumption and high-speed data processing. Here's how:

Energy-Efficient Spin-Orbit Torque (SOT) Devices: SOT devices rely on the AHE to generate spin currents, which can then switch the magnetization of a ferromagnetic layer. By maximizing the intrinsic AHE, these devices can operate with lower current densities, leading to reduced power consumption. This is particularly important for mobile and energy-constrained applications.

Fast Spin-to-Charge Conversion: The inverse AHE, where a spin current generates a transverse voltage, is crucial for reading out spin information in spintronic devices. A larger AHE translates to a more efficient conversion of spin currents into detectable voltage signals, enabling faster data read speeds.

AHE-Based Magnetic Sensors: AHE sensors offer high sensitivity and low noise levels for detecting magnetic fields. By enhancing the AHE, these sensors can achieve even greater sensitivity, enabling the detection of weaker magnetic fields. This has implications for applications ranging from magnetic storage read heads to biomedical imaging.

Low-Dissipation Spin Hall Effect (SHE) Materials: While not directly AHE-based, materials exhibiting a large AHE often also show a strong SHE, which is crucial for generating pure spin currents. Controlling the AHE through material engineering can indirectly lead to the discovery of new materials with a robust SHE, further benefiting spintronic applications.

Beyond Binary Data Storage: The AHE's sensitivity to the magnetization state could be exploited for developing multi-level memory cells, moving beyond the limitations of binary data storage (0 and 1). This could lead to higher storage densities and potentially faster data access times.
In conclusion, the ability to manipulate the AHE, particularly by enhancing the intrinsic contribution and suppressing the extrinsic one, holds significant promise for advancing spintronic technology. This control paves the way for developing devices with improved energy efficiency, faster processing speeds, and enhanced functionality, ultimately contributing to the realization of next-generation low-power, high-performance electronics.