Possibility of ferro-octupolar order in BaCaOsO assessed by X-ray magnetic dichroism measurements

芝田 悟朗 ; 藤森 淳; 他10名*

Shibata, Goro; Fujimori, Atsushi; 10 of others*

We studied the cubic double perovskite BaCaOsO containing the Os () ions, which exhibits a phase transition to a `hidden order' below K, by X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) at the Os edge. The cubic ligand-field splitting between the and levels of Os was deduced by XAS to be eV. The temperature dependence of the XMCD spectra was consistent with a meV residual cubic splitting of the lowest multiplet state into the non-Kramers doublet ground state and the triplet excited state. Ligand-field (LF) multiplet calculation under fictitious strong magnetic fields indicated that the exchange interaction between nearest-neighbor octupoles should be as strong as meV if a ferro-octupole order is stabilized in the `hidden-ordered' state, consistent with the exchange interaction of meV previously predicted theoretically using model and density functional theory calculations.