Effect of oxygen non-stoichiometry on magnetic and electrical transport properties of La_0.67Sr_0.33MnO₃

The effect of oxygen deficiency and oxygen excess on the magnetic and electrical transport properties of La_0.67Sr_0.33MnO₃ has been investigated. The thermal and isothermal magnetization measurement results show that the Curie temperature and saturation magnetization of oxygen deficient sample (defined as A) are higher than those oxygen excess sample (defined as B). The electrical resistivity of A is lower than that of B in studied temperature range. The magnetoresistance (MR) of B is larger than that of A in the temperature range from 280 to 360 K, which agrees with the magnetic field needed full spin polarization at room temperature. The colossal MR (CMR) around transition temperature from ferromagnetic metal to paramagnetic insulator (T_MI) for A is larger than that for B, which arises from assistance of stronger lattice deformation for A.