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The magnetocaloric effect (MCE) and electric-dielectric properties of the Nd-cobaltate perovskites Nd 0.6 Sr 0.4 Co 1Àx Mn x O 3 (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 (Mn 4+ /Mn 3+) 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 Â 10 À3) for Nd 0.6 Sr 0.4 MnO 3. 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 T C 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 DS M and the relative cooling power (RCP), and the maximum value is found for Nd 0.6 Sr 0.4 Co 0.3 Mn 0.7 O 3. These results compare favorably with those reported for similar materials, indicating our materials as a possible candidate for use in magnetocaloric refrigerators.

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