Magnetic properties of electron-doped LaCoO₃

We studied electron-doped LaCo_1-yTe⁶⁺_yO₃ by magnetization measurements and neutron scattering. The effective Bohr magneton, estimated by Curie–Weiss fitting around room temperature, is independent of y. This suggests that magnetic Co^3+(HS), not nonmagnetic Co^3+(LS), is mainly replaced by doped magnetic Co^2+(HS). At the lowest temperatures, a Brillouin-function-like saturating behavior persists in the magnetization curves even in the high-y samples, and neither a clear magnetic reflection nor magnetic dispersion is observed by neutron scattering. These findings indicate that the magnetic correlation is very weak, in contrast to the well-known hole-doped LaCoO₃ accompanied by a drastic transition to a ferromagnetic metal. However, we also found that the low-y samples exhibit nonnegligible enhancement of the saturated magnetization by ~2μB per a doped electron. All these characteristics are discussed in the light of the activation and inactivation of a spin-state blockade.