Spin fluctuations in oxygen doped layered perovskite cobalt oxide
中島 健次 ; 梶本 亮一 ; 山田 和芳*; 堀金 和正*
Nakajima, Kenji; Kajimoto, Ryoichi; Yamada, Kazuyoshi*; Horigane, Kazumasa*
Carrier doping into transition metal oxides triggers various phenomena, which have been subjected to intensive investigations. Layered oxide LaMO (M: 3d metal) is one of the model systems for such studies. In cobalates, contribution of orbital moment and possible spin state of Co give further complexity. In LaSrCoO, charges order in checker-board style and Co spin correlations are modulated in momentum space by the ordered charges. (1) Magnetic excitations in this system are reported to be accounted for spin-waves of Co spins taking into account the orbital moment. (2) In this study, we have investigated magnetic excitations in another almost half-doped system LaCoO by inelastic neutron scattering. Clear spin-wave excitations consistent to previous report on LaSrCoO were observed. However, we also observed an additional excitations with different zone center positions as well as excitation with higher spin-wave velocity. We expect detail analysis of present results can provide a key clue to understand the mechanism of complicated magnetic excitations caused by doped carrier, spin-orbital coupling and spins in transition metal oxides.