Study of a Magnetic Semiconductor La_0.8Ba_0.2Mn_1-xCu_xO₃(x = 0-0.2) and Its Giant MR

Abstract

Polycrystailine La_0.8Ba_0.2Mn_1-xCu_xO₃(x = 0-0.2) was successfully synthesized by using a standard solid reaction method. The crystal structure was shown to change from orthorhombic to tetragonal symmetry at x∼0.1. The magnetization, electric resistivity and MR were studied in relation with Cu doping level. It was also shown that, as x increases from 0 to 0.2, three kinds of MR were observed: spin-tunneling-type MR over the temperature range below T_c, a giant MR due to thermal spin fluctuation at T_c, and ordinary MR due to spin scattering of ferromagnet T_c.