Magnetic and Magnetoresistive Properties of Nanocrystalline Pr1-xAxMn1-yCoyO3 (A = Sr, Ca; x=0.3, y=0.5)

Nanocrystalline Pr(1-x)A(x)Mn(1-y)Co(y)O(3) (A = Sr, Ca; x = 0.3, y = 0.5) samples are prepared by sol-gel method. The XRD pattern show single phase and cubic crystal structure with a (=b=c) = 3.862 nm at room temperature. The crystallite size of the samples are calculated using Scherrer formula and found to be 15 nm and 24 nm for Pr0.7Sr0.3Mn0.5Co0.5O3 and Pr0.3Ca0.3Mn0.5Co0.5O3 respectively. The SEM images show the particles are spherical in shape and average particles sizes are about similar to 20 nm and similar to 25 nm. The samples undergo paramagnetic to ferromagnetic transition about similar to 172 K and similar to 153 K. The temperature dependence of resistivity (rho) data show insulating behaviour below 80 K and from 80 K to 300 K, the samples behave like semiconductor. Variable range hopping conduction is found to be dominating for temperatures above 80 K. The maximum magnetoresistance is found to be similar to 35 % and similar to 24 % at 100 K and it has negative sign.