Magnetic states at the surface of α-Fe2O3 thin films doped with Ti, Zn, or Sn
Magnetic states at the surface of α-Fe2O3 thin films doped with Ti, Zn, or Sn
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DOI：
10.1103/physrevb.96.094426
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发表时间：
2017-09-20
影响因子：
3.7
通讯作者：
Rothschild, Avner
中科院分区：
文献类型：
--
作者：
Ellis, David S.;Weschke, Eugen;Rothschild, Avner
用X射线磁线性二向色性（XMLD）谱研究了未掺杂和掺杂1%Ti、Sn或Zn的赤铁矿外延薄膜表面的自旋态。在未掺杂（T-M约为200 K）和Sn掺杂（T-M约为300 K）的情况下观察到桑色素转变，而Zn和Ti掺杂的样品总是分别处于高温和低温相。与已经报道的掺杂有四价离子Sn 4+和Ti 4+的大块赤铁矿的T-M显著降低相比，这些掺杂剂显著增加薄膜中的T-M，远远超过大块值。当T <T-M时，标准化的Fe L-II边二向色性与掺杂和温度无关，但当T <100 K时，峰振幅明显增加。我们观察到磁场诱导的二向色峰反转。通过在Ti掺杂样品上施加6.5T的磁场，实现了到T> T-M状态的转变。详细地表征了Sn掺杂样品的临界场随温度的变化关系。结果表明，样品到样品的Fe L-III-边缘光谱的变化，在很大程度上，仅由自旋取向状态。基于自旋多重态模型的偏振相关光谱的计算结果与实验结果吻合较好，并显示出峰结构的混合激发特征。
The spin states at the surface of epitaxial thin films of hematite, both undoped and doped with 1% Ti, Sn, or Zn, respectively, were probed with x-ray magnetic linear dichroism (XMLD) spectroscopy. Morin transitions were observed for the undoped (T-M approximate to 200 K) and Sn-doped (T-M approximate to 300 K) cases, while Zn-and Ti-doped samples were always in the high-and low-temperature phases, respectively. In contrast to what has been reported for bulk hematite doped with the tetravalent ions Sn4+ and Ti4+, for which T-M dramatically decreases, these dopants substantially increase T-M in thin films, far exceeding the bulk values. The normalized Fe L-II-edge dichroism for T < T-M does not strongly depend on doping or temperature, except for an apparent increase of the peak amplitudes for T < 100 K. We observed magnetic field-induced inversions of the dichroism peaks. By applying a magnetic field of 6.5 T on the Ti-doped sample, a transition into the T > T-M state was achieved. The temperature dependence of the critical field for the Sn-doped sample was characterized in detail. It was demonstrated the sample-to-sample variations of the Fe L-III-edge spectra were, for the most part, determined solely by the spin orientation state. Calculations of the polarization-dependent spectra based on a spin-multiplet model were in reasonable agreement with the experiment and showed a mixed excitation character of the peak structures.