The effective magnetic moments of Co2+ and Co3+ in SrTiO3 investigated by temperature-dependent magnetic susceptibility

Abstract The magnetic behavior of Co2+ and Co3+ ions doped into a well-known perovskite, SrTiO3, is investigated. We report the change in the effective magnetic moment of the cobalt ions, based on temperature-dependent magnetic susceptibility measurements, as a function of their formal valence. A low Co content (4%) is chosen to minimize the effects of Co-Co interactions and the co-dopant Nb5+ is employed to control the Co valence. The materials have formulas SrTi0.96-xCo0.04NbxO3, with x between x = 0.04 (Co3+) and x = 0.08 (Co2+). Both standard Curie-Weiss analysis and Kotani-type analysis reach the same conclusions: neither Co2+ nor Co3+ is in a low moment magnetic state when doped into SrTiO3, and no temperature-induced spin state transitions are observed.