Magnetic and Magnetoresistive Properties of Double Perovskite Oxides RE-SrMnCoO $_{6}$ (RE = Nd, La)

Polycrystalline samples of NdSrMnCoO₆ and LaSrMnCoO₆ have been synthesized by sol-gel technique and were characterized by means of X-ray diffraction (XRD). The Rietveld refinement of the XRD data confirms the single phase nature of the samples. These oxides have cubic crystal structure (space group Fm3macrm) at room temperature. The magnetization data measured in a field of 100 Oe, under zero field cooled and field cooled conditions, show thermomagnetic irreversibility below 210 K. The electrical resistivity of these samples increase with decreasing temperature from 300 K down to 80 K. The conduction above 115 K can be described by variable range hopping mechanism. A maximum magnetoresistance (MR) of about 5% and 11% are achieved at 90 K in an applied field of 7 T for NdSrMnCoO₆ and LaSrMnCoO₆ samples, respectively, and MR has a negative sign.