Structural, magnetic and transport study of monovalent Na-doped manganite Pr0.55Na0.05Sr0.4MnO3

Abstract The manganite Pr 0.55 Na 0.05 Sr 0.4 MnO 3 prepared by solid state reaction has the orthorhombic structure and mean crystallite size of 51 nm. Scanning electron microscopy (SEM) shows that the grains are irregularly spherical like shaped with sizes 400 to 700 nm. In vicinity of Curie temperature equal to 289 K the magnetic entropy change |Δ SM max | attains 1.75 J kg −1  K −1 under an applied magnetic field of 2 T which corresponds to relative cooling power of 93 J/kg. Electrical resistivity measurements reveal a transition from metallic to semiconductor phase. Temperature variation of electrical resistivity was fitted by the small polaron hopping (SPH) and Mott’s Variable range Hopping (VRH) models. The activation energy and Mott temperature are found to decrease and N ( E F ) to increase in magnetic field varying from zero to 1 T. The phonon contribution dominates in thermal conductivity.