Study of magnetic and electrical properties of Pr0.65Ca0.25Ba0.1MnO3 manganite

摘要

The magnetic properties and magnetocaloric effect (MCE) in Pr0.65Ca0.25Ba0.1MnO3 have been investigated supplemented by electrical data. X-ray diffraction shows that the sample crystallizes in the distorted orthorhombic system with the Pnma space group. Pr0.65Ca0.25Ba0.1MnO3 undergoes paramagnetic-ferromagnetic (PM-FM) phase transition at T-C approximate to 85 K. For a magnetic field change of 5 T, the maximum value of the magnetic entropy change (-SmaxM) is estimated to be 4.4 J kg(-1) K-1 around T-C with a large relative cooling power (RCP) value of 263.5 J kg(-1). While the modified Arrott plots suggested that the magnetic transition belongs to the second order phase transitions, the universal curves of the rescaled magnetic entropy (S-M) proved the opposite. The electrical properties of Pr0.65Ca0.25Ba0.1MnO3 have been investigated using impedance spectroscopy techniques. The dc-resistivity (sigma(dc)) study shows the presence of semiconductor behavior. Ac-conductivity (sigma(ac)) analysis shows that the conductivity is governed by a hopping process. From the analysis of the alternating regime, the exponent s variation obtained is in good agreement with Mott theory. The impedance spectrum analysis reveals the presence of a relaxation phenomenon. Based on these analyzes, the sample can be modeled by an electrical equivalent circuit.