Photoemission studies of magnetic semiconductors

*对脉冲激光沉积（PLD）法制备的Zn1-xCoxO （x=0.05）的Co 2p核心吸收边进行了软x射线吸收（XAS）和软x射线磁圆二色性（XMCD）研究，并利用聚类模型计算对所得光谱进行了分析。我们发现XMCD强度对温度和磁场的依赖与非相互作用的Co离子有很大的不同，Co离子之间的铁磁和反铁磁相互作用不均匀地共存。*采用分子束外延（MBE）法制备Ga1-xMnxN，对其Mn 2p核心吸收边进行了XAS和共振光发射研究，并利用团簇模型计算对所得光谱进行了分析。我们发现Mn离子的价态为2+，并且Mn三维态大部分分布在GaN宿主的价带内。发现Mn掺杂在价带最大值Mn以上形成的受体能级被占据了b…更多的y电子，说明由于补偿效应，理论预测的高温铁磁性没有实现。*在Ga1-xCrxN （x=0.015）的cr2p核心吸收边进行了XAS、XMCD和共振光发射研究。cr2p XAS光谱表明，Cr处于3+价态。与Ga1-xMnxN形成鲜明对比的是，Cr三维偏态密度（PDOS）主要分布在GaN的带隙内。发现Cr 3d PDOS在费米能级被抑制，并且没有观察到由能带结构计算预测的费米边缘特征。* Zn1-xVxO （x=0.05）表现出弱铁磁性，XAS和XMCD测量。发现取代Zn2+的V离子是导致磁性能的原因。从XMCD谱与磁化率的比较中，我们发现10%的V离子是顺磁性的，90%的V离子是强反铁磁性的。此外，还发现顺磁性V离子受到六方ZnO主体轴向晶体场的影响。少

* Soft x-ray absorption (XAS) and soft x-ray magnetic circular dichroism (XMCD) studies at the Co 2p core absorption edges of Zn1-xCoxO (x=0.05) prepared by the pulsed laser deposition (PLD) method were performed and the obtained spectra were analyzed using cluster-model calculations. We have found that the temperature and the magnetic field dependences of the XMCD intensity were very different from non-interacting Co ions and that ferromagnetic and antiferromagnetic interactions between the Co ions coexist inhomogeneously.* XAS and resonance photoemission studies at the Mn 2p core absorption edges of Ga1-xMnxN prepared by the molecular-beam epitaxy (MBE) method were performed, and the obtained spectra were analyzed using cluster-model calculations. We found that the valence of the Mn ion was 2+ and that the Mn 3d states were largely distributed within the valence band of the GaN host. Acceptor levels formed by the Mn doping above the valence-band maximum Mn were found to be occupied b … More y electrons, indicating that the high-temperature ferromagnetism predicted by theory was nor realized because of the compensation effect.* XAS, XMCD and resonance photoemission studies were performed at the Cr 2p core absorption edges of Ga1-xCrxN (x=0.015). The Cr 2p XAS spectra indicated that the Cr was in the 3+ valence state. The Cr 3d partial density of states (PDOS) were largely distributed within the band gap of GaN, in striking contrast with Ga1-xMnxN. The Cr 3d PDOS was found to be suppressed at the Fermi level, and no Fermi-edge feature as predicted by band-structure calculations was observed.* XAS and XMCD measurements were made on Zn1-xVxO (x=0.05) which exhibited weak ferromagentism. The V ions substituting Zn2+ were found to be responsible for the magnetic properties. From comparison of the XMCD spectra with the magnetic susceptibility, we found that 10% of V ions were paramagnetic and 90 % were strongly coupled with each other antiferromagnetically. Furthermore, the paramagnetic V ions were found to be influenced by the axial crystal field of the hexagonal ZnO host. Less