近日，课题组和合作者在稀土铁石榴石薄膜的磁化翻转机制研究方面取得重要进展。研究团队通过自旋霍尔磁电阻（SMR）测量，在Pt/Tm₃Fe₅O₁₂（TmIG）异质结中观测到异常的电阻跳变行为，并利用三维Stoner-Wohlfarth模型成功重构了磁化翻转的三维轨迹。相关成果以“Cubic magnetocrystalline anisotropy-driven spin reorientation in TmIG detected by spin Hall magnetoresistance”为题发表于Chinese Physics B(Chin. Phys. B 35, 087202 (2026))。

  研究团队采用脉冲激光沉积法制备了高质量(111)取向TmIG薄膜并构建Pt/TmIG异质结，输运测量显示在100 K以下的SMR曲线在面外磁场扫描中呈现阶跃式跳变特征，结合三维Stoner-Wohlfarth模型模拟证实该异常行为源于磁化翻转过程中面内方位角的离散跳变。研究表明，立方磁晶各向异性在(111)面内具有3m旋转对称的能量势景，该势景迫使磁矩翻转过程时发生60°或120°的方位角跳变以沿低能路径演化，进而导致SMR曲线多次跳变。温度依赖测量表明，随温度降低，立方磁晶各向异性和磁弹各向异性均显著增强，跳变临界场和饱和场同步增大，但能量势景的拓扑结构保持不变。

  该工作不仅揭示了立方磁晶各向异性在(111)取向稀土铁石榴石薄膜中驱动复杂自旋重取向的核心作用，还展示了SMR作为三维磁化状态无损探测工具的独特优势。这一发现为基于磁晶各向异性工程的自旋逻辑器件和多态存储器设计提供了新的物理基础。

Recently, our group in collaboration with partners, has made significant progress in the study of the magnetization reversal mechanism in rare-earth iron garnet thin films. By employing spin Hall magnetoresistance (SMR) measurements, we observed anomalous resistance jump behavior in Pt/Tm₃Fe₅O₁₂ (TmIG) heterostructures and successfully reconstructed the three-dimensional magnetization reversal trajectory using a three-dimensional Stoner-Wohlfarth model. The related work is published in Chinese Physics B under the title "Cubic magnetocrystalline anisotropy-driven spin reorientation in TmIG detected by spin Hall magnetoresistance" (Chin. Phys. B 35,087202 (2026)).

We prepared high-quality (111)-oriented TmIG thin films by pulsed laser deposition and constructed Pt/TmIG heterostructures. Transport measurements revealed step-like jump features in the SMR curves during out-of-plane magnetic field sweeps below 100K. Combined with three-dimensional Stoner-Wohlfarth model simulations, it was confirmed that this anomalous behavior originates from discrete in-plane azimuthal angle jumps during the magnetization reversal process. Further investigation shows that the cubic magnetocrystalline anisotropy exhibits a 3m-symmetric energy landscape in the (111) plane, which forces the magnetization to undergo 60° or 120° azimuthal jumps to follow low-energy paths, resulting in multiple jumps in the SMR curves. Temperature-dependent measurements indicate that as temperature decreases, both the cubic magnetocrystalline anisotropy and magnetoelastic anisotropy increase significantly, leading to synchronous increases in the critical fields for jumps and the saturation field, while the topological structure of the energy landscape remains unchanged.

This work not only reveals the central role of cubic magnetocrystalline anisotropy in driving complex spin reorientation in (111)-oriented rare-earth iron garnet thin films but also demonstrates the unique advantage of SMR as a non-destructive probe for three-dimensional magnetization states. These findings provide a new physical foundation for the design of spin logic devices and multistate memory devices based on magnetocrystalline anisotropy engineering.

图1. 采用三维Stoner-Wohlfarth模型模拟的磁化轨迹。(a) 磁场扫描过程中磁化矢量的三维轨迹。蓝色和红色曲线分别代表反向和正向扫场。赤道面（θ_M = 90°）以灰色阴影表示，并以60°间隔绘制了径线。蓝色和红色虚线箭头表示自旋重取向方向。蓝红交替的线段表示反向和正向扫场路径中的轨迹重叠部分。(b) 立方磁晶各向异性的能量势景（K_c1 = −1.25 kJ⋅m⁻³，K_c2 = 0.48 kJ⋅m⁻³）。赤道面以灰色显示，红色箭头表示正向扫场过程中的磁化矢量轨迹。(c) 磁场扫描过程中相对总能量随φ_M和θ_M变化的极坐标图。极角θ_M映射到了极经上（r = θ_M/180°），极坐标中心和圆周分别代表θ_M = 0°和180°。对于每个θ_M，统一计算了所有φ_M值对应的总能量，并归一化后映射到颜色标尺上。

  论文第一作者为硕士生余庆汇，共同通讯作者为南洋理工大学丁石磊助理教授和华南理工大学吴锐教授。论文链接：https://cpb.iphy.ac.cn/article/doi/10.1088/1674-1056/ae5a14