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

Magnetic entropy change (ΔSM), magnetoresistance (MR) and resistivity (ρ) have been studied in a series of bulk polycrystalline manganites (La1−xGdx)0.67Sr0.33MnO3 (x = 0.1-0.7) with fixed carrier concentration. These effects, as well as the Curie temperature Tc, are all influenced much by the average ionic radius of the La site , 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 |ΔSM| at Tc 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%.