Field-induced magnetic anisotropy in La_0.7Sr_0.3CoO₃

Abstract

Magnetic anisotropy has been measured for the ferromagnetic La0.7Sr0.3CoO3\nperovskite from an analysis of the high-field part of the magnetization vs.\nfield curves, i.e., the magnetic saturation regime. These measurements give a\nmagnetic anistropy one order of magnitude higher than that of reference\nmanganites. Surprisingly, the values of the magnetic anisotropy calculated in\nthis way do not coincide with those estimated from measurements of coercive\nfields which are one order of magnitude smaller. It is proposed that the reason\nof this anomalous behaviour is a transition of the trivalent Co ions under the\nexternal magnetic field from a low-spin to an intermediate-spin state. Such a\ntransition converts the Co3+ ions into Jahn-Teller ions having an only\npartially quenched orbital angular momentum, which enhances the intra-atomic\nspin-orbit coupling and magnetic anisotropy.\n