Critical field analysis and magnetic properties of perovskite manganese oxide La0.8Ca0.2Mn1-xNixO3(x = 0.0,0.1,0.2)

Abstract

Critical field analysis and the magnetocaloric effect of the polycrystalline perovskite manganese oxide samples, La0.8Ca0.2Mn1-xNixO3 (x = 0.0,0.1,0.2), which were prepared using a traditional solid phase reaction method, were explored. The data obtained from X-ray diffraction (XRD) measurements of the polycrystalline samples show good single-phase properties. The replacement of a given Mn3+ ion fraction by Ni2+ions decreased the crystal parameters and unit cell volume, Curie temperature (Tc), and the magnetic and the magnetic entropy change. These property changes originate from the partial substitution of Mn3+ ions by Ni2+, which changes the Mn3+/Mn4+ ratio and consequently weakens the double exchange (DE) effect. At an applied magnetic field of 7 T, the maximum difference in magnetic entropy of the undoped sample is 6.15 J/kg•K, and the refrigeration efficiency is 422.94 J/kg. The critical parameters of the parent material and the doped sample fit well to the Tricritical model. The La0.8Ca0.2Mn1-xNixO3 samples with x = 0.0 exhibit crossover of the phase transitions, which can be first or second order. The observed phase transitions of samples with x = 0.1 and 0.2 are exclusively second order. Around the TC of La0.8Ca0.2Mn1-xNixO3 (x = 0.0, 0.1 and 0.2) compounds, the correlation of the magnetic field with the maximum change in magnetic entropy follows a power law.