Magnetic entropy change and magnetotransport in Gd doped La–Sr–Mn–O perovskite

Abstract

Magnetic entropy change (Δ S M), magnetoresistance (MR) and resistivity ( ρ) have been studied in a series of bulk polycrystalline manganites (La 1− x Gd x ) 0.67Sr 0.33MnO 3 ( x = 0.1–0.7) with fixed carrier concentration. These effects, as well as the Curie temperature T c, are all influenced much by the average ionic radius of the La site < r A>, which decreases monotonously with the increase of the Gd content. As the doping level x increases, a structural phase transition from rhombohedral to orthorhombic is also observed in these samples. For the x = 0.6 sample, the maximum |Δ S M| at T c in a field change of 10 Oe is 3.2 J/kg K, and for the x = 0.7 sample, the maximum MR in a magnetic field of 40 kOe is 27,700%.