Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator
Coexistence of Surface and Bulk Ferromagnetism Mimics Skyrmion Hall Effect in a Topological Insulator
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DOI：
10.1103/physrevx.10.011012
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发表时间：
2020-01-17
影响因子：
12.5
通讯作者：
Molenkamp, L. W.
中科院分区：
文献类型：
--
作者：
Fijalkowski, K. M.;Hartl, M.;Molenkamp, L. W.
本文报道了磁掺杂拓扑绝缘体（V，Bi，Sb）（2）Te-3中的反常霍尔效应。我们发现它包含两个相反符号的贡献。这两个组件被发现依赖于不同的载流子密度，导致作为施加的栅极电压的函数的总的异常霍尔效应的符号反转。这两个贡献被发现有不同的磁化反转场，这与温度相关的研究指向共存的两个铁磁订单的系统中。此外，我们发现系统的总反常霍尔响应的符号依赖于磁性层的厚度和磁性掺杂浓度。的厚度依赖性表明，这两个铁磁成分起源于表面和本体的磁性拓扑绝缘体膜。我们相信，我们的观测提供了对磁性行为的深入了解，从而有助于最终理解这种材料的磁性起源。此外，我们的数据与通常与skyrmion贡献相关的异常霍尔信号有惊人的相似之处。我们的分析提供了一个简单的解释磁场依赖的霍尔信号和观察到的符号变化，而不需要调用skyrmion，从而表明，需要谨慎时，从skyrmion阶段的影响索赔。
Here, we report the investigation of the anomalous Hall effect in the magnetically doped topological insulator (V, Bi, Sb)(2)Te-3. We find it contains two contributions of opposite sign. Both components are found to depend differently on carrier density, leading to a sign inversion of the total anomalous Hall effect as a function of applied gate voltage. The two contributions are found to have different magnetization reversal fields, which in combination with a temperature dependent study points towards the coexistence of two ferromagnetic orders in the system. Moreover, we find that the sign of total anomalous Hall response of the system depends on the thickness and magnetic doping density of the magnetic layer. The thickness dependence suggests that the two ferromagnetic components originate from the surface and bulk of the magnetic topological insulator film. We believe that our observations provide insight into the magnetic behavior, and thus will contribute to an eventual understanding of the origin of magnetism in this material class. In addition, our data bear a striking resemblance to anomalous Hall signals often associated with skyrmion contributions. Our analysis provides a straightforward explanation for both the magnetic field dependence of the Hall signal and the observed change in sign without needing to invoke skyrmions, and thus suggest that caution is needed when making claims of effects from skyrmion phases.