Thermal nucleation and high-resolution imaging of submicrometer magnetic bubbles in thin thulium iron garnet films with perpendicular anisotropy
Thermal nucleation and high-resolution imaging of submicrometer magnetic bubbles in thin thulium iron garnet films with perpendicular anisotropy
复制标题
DOI：
10.1103/physrevmaterials.4.011401
复制
发表时间：
2020-01-28
影响因子：
3.4
通讯作者：
Beach, Geoffrey S. D.
中科院分区：
文献类型：
--
作者：
Buttner, Felix;Mawass, Mohamad A.;Beach, Geoffrey S. D.
亚铁磁性铁石榴石具有超低阻尼和零电流分流的特性，是自旋电子学应用中很有前途的材料。最近发现，一些nm厚的石榴石膜与重金属界面也可以表现出相当大的界面自旋轨道相互作用，导致一维手性畴壁的出现和有效的电控制。相比之下，二维气泡到目前为止只在微米厚的薄膜中得到证实。在这里，我们表明，通过高分辨率扫描透射X射线显微镜和光发射电子显微镜，亚微米气泡可以成核和稳定在类似的25 nm厚的铥铁石榴石薄膜通过短的热脉冲产生的电流在相邻的Pt条，或通过超快激光照明。我们还发现，准静态过程不会导致气泡状态的形成，这表明达到该状态的热力学路径需要瞬态动力学。X射线成像显示，气泡具有随机手性和拓扑结构的布洛赫型壁，表明在这里研究的石榴石膜厚度的手性相互作用可以忽略不计。热成核的鲁棒性和这里展示的可行性，图像石榴石为基础的设备，通过X射线在传输几何结构和灵敏度的畴壁手性是关键步骤，使小自旋纹理和动力学的研究在垂直磁化的薄膜石榴石。
Ferrimagnetic iron garnets are promising materials for spintronics applications, characterized by ultralow damping and zero current shunting. It has recently been found that few nm-thick garnet films interfaced with a heavy metal can also exhibit sizable interfacial spin-orbit interactions, leading to the emergence, and efficient electrical control, of one-dimensional chiral domain walls. Two-dimensional bubbles, by contrast, have so far only been confirmed in micrometer-thick films. Here, we show by high resolution scanning transmission x-ray microscopy and photoemission electron microscopy that submicrometer bubbles can be nucleated and stabilized in similar to 25-nm-thick thulium iron garnet films via short heat pulses generated by electric current in an adjacent Pt strip, or by ultrafast laser illumination. We also find that quasistatic processes do not lead to the formation of a bubble state, suggesting that the thermodynamic path to reaching that state requires transient dynamics. X-ray imaging reveals that the bubbles have Bloch-type walls with random chirality and topology, indicating negligible chiral interactions at the garnet film thickness studied here. The robustness of thermal nucleation and the feasibility demonstrated here to image garnet-based devices by x-rays both in transmission geometry and with sensitivity to the domain wall chirality are critical steps to enabling the study of small spin textures and dynamics in perpendicularly magnetized thin-film garnets.