Role of nickel doping on magnetocaloric properties of La0.7Sr0.3Mn1-xNixO3 manganites

This study reports the effect of Ni substitution for Mn on structural, magnetic, and magnetocaloric properties of La0.7Sr0.3MnO3 manganite synthesized by sol-gel technique. The structural, morphological, and magnetic properties are investigated using x-ray diffractometer (XRD), scanning electron microscope (SEM), and vibrating sample magnetometer (VSM) systems. XRD results showed that all samples crystallize in rhombohedral structure. Thermomagnetic measurements showed that T-C decreases with the addition of Ni from 363 K for x = 0.00 to 324 K for x = 0.06. Delta S-M determined by Maxwell's relations and Landau theory gave compatible results in the transition temperature and region above. Delta SM (max) values were determined as 4.52, 4.51, 4.41, and 3.90 J kg(-1) K-1 for x = 0.00, 0.02, 0.04, and 0.06 at 5T, respectively. The Arrott plots and the scaling analysis of Delta S-M, which collapsed on a single curve, showed that magnetic transitions are of second order.