Temperature features of magnetoresistance of layered manganite La 2Sm 0.4Sr 0.6Mn 2O 7

Abstract

Bulk polycrystalline layered perovskite sample La 2Sm 0.4Sr 0.6Mn 2O 7 was prepared by the conventional solid-state reaction technique. Temperature dependence of magnetization measurements in the zero-field-cooled and field-cooled conditions with an applied magnetic field of 100 Oe indicates that layered manganite La 2Sm 0.4Sr 0.6Mn 2O 7 undergoes a paramagnetic to ferromagnetic transition at Curie temperature T c∼355 K. The magnetic transition temperature ( T c) is much higher than metal–insulator transition temperature ( T p) obtained from temperature dependence resistivity measurement. The anisotropic exchange interaction may be one of the reasons resulting in a large deviation between T c and T p. Field dependence of magnetization measurements showed a high value of magnetization (62 emu/g at 5 K and 42 emu/g at 300 K) in an applied magnetic field of 1 T. At 78 K, a sharp increase of magnetoresistance was observed at low magnetic fields followed by a weak and linear dependence at high fields.