Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland.
Institute of Physics, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
Nat Commun. 2016 Oct 21;7:13071. doi: 10.1038/ncomms13071.
Entanglement of the spin-orbit and magnetic order in multiferroic materials bears a strong potential for engineering novel electronic and spintronic devices. Here, we explore the electron and spin structure of ferroelectric α-GeTe thin films doped with ferromagnetic Mn impurities to achieve its multiferroic functionality. We use bulk-sensitive soft-X-ray angle-resolved photoemission spectroscopy (SX-ARPES) to follow hybridization of the GeTe valence band with the Mn dopants. We observe a gradual opening of the Zeeman gap in the bulk Rashba bands around the Dirac point with increase of the Mn concentration, indicative of the ferromagnetic order, at persistent Rashba splitting. Furthermore, subtle details regarding the spin-orbit and magnetic order entanglement are deduced from spin-resolved ARPES measurements. We identify antiparallel orientation of the ferroelectric and ferromagnetic polarization, and altering of the Rashba-type spin helicity by magnetic switching. Our experimental results are supported by first-principles calculations of the electron and spin structure.
在多铁材料中，自旋轨道和磁有序的纠缠具有很大的潜力，可以用于设计新型电子和自旋电子器件。在这里，我们研究了掺铁磁 Mn 杂质的铁电α-GeTe 薄膜的电子和自旋结构，以实现其多铁功能。我们使用体敏感软 X 射线角分辨光电子能谱（SX-ARPES）来跟踪 GeTe 价带与 Mn 掺杂剂的杂化。随着 Mn 浓度的增加，我们观察到在狄拉克点附近的体 Rashba 能带中，磁场逐渐打开，这表明存在铁磁有序，同时 Rashba 劈裂保持不变。此外，从自旋分辨 ARPES 测量中可以推断出自旋轨道和磁有序纠缠的细微细节。我们确定了铁电极化和铁磁极化的反平行取向，以及通过磁开关改变 Rashba 型自旋螺旋度。我们的实验结果得到了电子和自旋结构的第一性原理计算的支持。
