Haverkort M W, Hu Z, Cezar J C, Burnus T, Hartmann H, Reuther M, Zobel C, Lorenz T, Tanaka A, Brookes N B, Hsieh H H, Lin H-J, Chen C T, Tjeng L H
II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany.
Phys Rev Lett. 2006 Oct 27;97(17):176405. doi: 10.1103/PhysRevLett.97.176405. Epub 2006 Oct 26.
Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.
利用软X射线吸收光谱和钴L(2,3)边的磁圆二色性，我们揭示了LaCoO₃中的自旋态转变可以用低自旋基态和三重简并高自旋第一激发态很好地描述。从谱线形状的温度依赖性，我们发现有限温度下的LaCoO₃是一个非均匀混合自旋态系统。至关重要的是，顺磁态的磁圆二色性信号携带大量轨道动量。这直接表明目前被接受的低自旋或中间自旋图像存在差异。从这些光谱学得出的参数完全解释了现有的磁化率、电子自旋共振和非弹性中子数据。
