Field-induced magnetic anisotropy in

¹ Departamento de Física Aplicada, Universidade de Santiago de Compostela E-15782 Santiago de Compostela, Spain
² Instituto de Ciencia de Materiales, CSIC - E-28049, Madrid, Spain
³ Departamento de Física de la Materia Condensada-ICMA Universidad de Zaragoza-CSIC - E-50009 Zaragoza, Spain
⁴ Istituto Nazionale per la Fisica della Materia and Dipartimento di Fisica ed Ingegneria dei Materiali, Università di Ancona I-60131 Ancona, Italy
⁵ Departamento de Química Fundamental e Industrial, Universidade da Coruña E-15071 A Coruña, Spain

Received: 20 September 2002
Accepted: 7 March 2003

Abstract

Magnetic anisotropy has been measured for the ferromagnetic perovskite from an analysis of the high-field part of the magnetization vs. field curves, i.e., the magnetic saturation regime. These measurements give a magnetic anistropy one order of magnitude higher than that of reference manganites. Surprisingly, the values of the magnetic anisotropy calculated in this way do not coincide with those estimated from measurements of coercive fields which are one order of magnitude smaller. It is proposed that the reason of this anomalous behaviour is a transition of the trivalent Co ions under the external magnetic field from a low-spin to an intermediate-spin state. Such a transition converts the ions into Jahn-Teller ions having an only partially quenched orbital angular momentum, which enhances the intra-atomic spin-orbit coupling and magnetic anisotropy.