Temperature features of magnetoresistance of layered manganite La2Sm0.4Sr0.6Mn2O7

Bulk polycrystalline layered perovskite sample La2Sm0.4Sr0.6Mn2O7 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 La2Sm0.4Sr0.6Mn2O7 undergoes a paramagnetic to ferromagnetic transition at Curie temperature Tc∼355 K. The magnetic transition temperature (Tc) is much higher than metal-insulator transition temperature (Tp) obtained from temperature dependence resistivity measurement. The anisotropic exchange interaction may be one of the reasons resulting in a large deviation between Tc and Tp. 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.