Spin State Transition in LaCoO3 Studied Using Soft X-Ray Absorption Spectroscopy and Magnetic Circular Dichroism

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.