Study of magnetic and electrical properties of Pr_0.65Ca_0.25Ba_0.1MnO₃manganite

Abstract

The magnetic properties and magnetocaloric effect (MCE) in Pr_0.65Ca_0.25Ba_0.1MnO₃ have been investigated supplemented by electrical data. X-ray diffraction shows that the sample crystallizes in the distorted orthorhombic system with the <i>Pnma</i> space group. Pr_0.65Ca_0.25Ba_0.1MnO₃ undergoes paramagnetic-ferromagnetic (PM-FM) phase transition at <i>T</i> _C ∼ 85 K. For a magnetic field change of 5 T, the maximum value of the magnetic entropy change (-Δ<i>S</i> ^max _M) is estimated to be 4.4 J kg^-1 K^-1 around <i>T</i> _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 (Δ<i>S</i> _M) proved the opposite. The electrical properties of Pr_0.65Ca_0.25Ba_0.1MnO₃ have been investigated using impedance spectroscopy techniques. The dc-resistivity (<i>σ</i> _dc) study shows the presence of semiconductor behavior. Ac-conductivity (<i>σ</i> _ac) analysis shows that the conductivity is governed by a hopping process. From the analysis of the alternating regime, the exponent <i>s</i> 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.