Structural, magnetotransport, and magnetocaloric properties of La0.7Sr0.3−xAgxMnO3 perovskite manganites

The structural, magnetotransport, and magnetocaloric properties of monovalent (Ag) doped La0.7Sr0.3−xAgxMnO3 (x = 0.05, 0.1, 0.15, and 0.2) polycristalline perovskites have been reported. Our samples have been elaborated using the solid-state reaction at high temperature. All our synthesized samples are single phase and crystallize in the distorted rhombohedral system with R3¯c space group. Ag substitution leads to an increase of the unit cell volume from 348.4 Å3 for x = 0 to 353.4 Å3 for x = 0.2. Moreover, with decreasing temperature all our samples exhibit a paramagnetic to ferromagnetic transition and a semiconductor to metallic one. Furthermore, with increasing Ag content from zero to 0.2, the Curie temperature Tc shifts from 365 to 286 K as well as the saturated magnetization Msp from 3.31 to 3.2 μB/Mn and the electrical transition temperature Tρ varies from 340 to 260 K. A magnetoresistance ratio of about 48% at 300 K in a magnetic applied field of 8 T has been observed in La0.7Sr0.1Ag0.2MnO3 sample. In addition, a large magnetocaloric effect near Tc has been detected with a maximum of magnetoentropy change, ΔSmaxΔSmax, of 0.9 and 4.5 J/kg K at 1 and 7 T, respectively, for a substitution rate of 0.1.