Li Mingda, Chang Cui-Zu, Wu Lijun, Tao Jing, Zhao Weiwei, Chan Moses H W, Moodera Jagadeesh S, Li Ju, Zhu Yimei
Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Francis Bitter Magnet Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2015 Apr 10;114(14):146802. doi: 10.1103/PhysRevLett.114.146802. Epub 2015 Apr 9.
We demonstrate by high resolution low temperature electron energy loss spectroscopy (EELS) measurements that the long range ferromagnetic (FM) order in the vanadium- (V-)doped topological insulator Sb_{2}Te_{3} has the nature of van Vleck-type ferromagnetism. The positions and the relative amplitudes of two core-level peaks (L_{3} and L_{2}) of the V EELS spectrum show unambiguous change when the sample is cooled from room temperature to T=10 K. Magnetotransport and comparison of the measured and simulated EELS spectra confirm that these changes originate from the onset of FM order. Crystal field analysis indicates that in V-doped Sb_{2}Te_{3}, partially filled core states contribute to the FM order. Since van Vleck magnetism is a result of summing over all states, this magnetization of core level verifies the van Vleck-type ferromagnetism in a direct manner.
我们通过高分辨率低温电子能量损失谱（EELS）测量表明，钒（V）掺杂的拓扑绝缘体Sb₂Te₃中的长程铁磁（FM）序具有范弗莱克型铁磁性的性质。当样品从室温冷却到T = 10 K时，V EELS谱的两个芯能级峰（L₃和L₂）的位置和相对幅度显示出明确的变化。磁输运以及测量和模拟的EELS谱的比较证实，这些变化源于FM序的开始。晶体场分析表明，在V掺杂的Sb₂Te₃中，部分填充的芯态对FM序有贡献。由于范弗莱克磁性是对所有状态求和的结果，这种芯能级的磁化以直接的方式验证了范弗莱克型铁磁性。
