Magnetocaloric effect, electric, and dielectric properties of Nd0.6Sr0.4MnxCo1-xO3 composites

The magnetocaloric effect (MCE) and electric-dielectric properties of the Nd-cobaltate perovskites Nd0.6Sr0.4Co1-xMnxO3 (x = 0, 0.3, 0.7 and 1) were investigated for possible use in magnetic cooling applications. Upon Mn substitution, the magnetic exchange interaction is affected by the (Mn4+/Mn3+) ratio, which in turn impacts several physical properties. The XRD patterns of the synthesized composites revealed a single phase with an orthorhombic structure with space group Pbnm (62). The orthorhombic lattice distortion increases linearly with the Mn content, reaching a maximum value (D = 7.377 x 10(-3)) for Nd0.6Sr0.4MnO3. The temperature and frequency dependence of the dielectric permittivity was studied and analyzed using Maxwell-Wagner interfacial polarization and Koops phenomenological theory. The rapid increase in magnetic susceptibility around the paramagnetic (PM)-ferromagnetic (FM) transition temperature TC is greatly affected by Mn substitution. The decrease in susceptibility with increasing temperature can be attributed to a charge ordering effect. The PM-FM transition occurs in the temperature range of 150-200 K. Moreover, the presence of spontaneous magnetization with second-order phase transitions is observed from Arrott plot isotherms. The MCE was also investigated by determining Delta SM and the relative cooling power (RCP), and the maximum value is found for Nd0.6Sr0.4Co0.3 Mn0.7O3. These results compare favorably with those reported for similar materials, indicating our materials as a possible candidate for use in magnetocaloric refrigerators. (C) 2018 Elsevier B.V. All rights reserved.