Tyagi Shekhar, Sathe V G, Sharma Gaurav, Phase D M, Reddy V R
UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore-452001, India.
J Phys Condens Matter. 2020 Jul 15;32(30):305501. doi: 10.1088/1361-648X/ab8424. Epub 2020 Mar 27.
Enhanced magnetic moment and coercivity in SrRuO thin films are significant issues for advanced technological usages and hence are researched extensively in recent times. Most of the previous reports on thin films with enhanced magnetic moment attributed it to the high spin state. Our magnetization results show high magnetic moment of 3.3 μ/Ru ion in the epitaxial thin films grown on LSAT substrate against 1.2 μ/Ru ion observed in bulk compound. Contrary to the previous reports the Ru ions are found to be in low spin state and the orbital moment is shown to be contributing significantly in the enhancement of magnetic moment. We employed x-ray absorption spectroscopy and resonant valance band spectroscopy to probe the spin state and orbital contributions in these films. The existence of strong spin-orbit coupling responsible for the de-quenching of the 4d orbitals is confirmed by the observation of the non-statistical large branching ratio at the Ru M absorption edges. X-ray magnetic circular dichroism studies performed at the Ru M edges provided direct evidence of significant contribution of orbital moment in the film grown on LSAT. The relaxation of orbital quenching by strain engineering provides a new tool for enhancing magnetic moment and strain disorder is shown to be an efficient mean to control the spin-orbit coupling.
对于先进技术应用而言，SrRuO薄膜中增强的磁矩和矫顽力是重要问题，因此近年来得到了广泛研究。先前关于具有增强磁矩的薄膜的大多数报告将其归因于高自旋态。我们的磁化结果表明，在LSAT衬底上生长的外延薄膜中，Ru离子的磁矩高达3.3 μ/Ru离子，而在体相化合物中观察到的为1.2 μ/Ru离子。与先前的报告相反，发现Ru离子处于低自旋态，并且轨道矩在磁矩增强中起着重要作用。我们采用X射线吸收光谱和共振价带光谱来探测这些薄膜中的自旋态和轨道贡献。通过在Ru M吸收边观察到非统计性的大分支比，证实了导致4d轨道去淬灭的强自旋 - 轨道耦合的存在。在Ru M边进行的X射线磁圆二色性研究提供了直接证据，表明在LSAT上生长的薄膜中轨道矩有显著贡献。通过应变工程实现轨道淬灭的弛豫为增强磁矩提供了一种新工具，并且应变无序被证明是控制自旋 - 轨道耦合的有效手段。
