Structure, magnetic and magnetiocaloric properties in La1.4Sr1.6-xCaxMn2O7 perovskite compounds

The nominal compositions of La1.4Sr1.6 xCaxMn2O7 (0.0 <= x <= 1.6) have been synthesized using solid-state reaction method. The XRD analyses show that the compounds are pure 14/mmm tetragonal bilayered perovskites phase for x <= 0.8, while they are mixture of a main orthorhombic ABO(3)-type perovskite and a slight cubic calcium oxide for x >= 1.0. For lightly doped samples (x <= 0.8), the 3D ferromagnetic (FM) transition temperature first declines and then disappears due to the depression of the interlayer exchange interaction by Ca2+ doping. However, the intralayer exchange interaction is strengthened in the x = 0.4 sample on account of large Jahn-Teller distortion of MnO6 octahedra. A large magnetic entropy change of 2.28 J kg(-1) K-1 is obtained in the nominal composition La1.4Sr1.6 xCaxMn2O7 (x = 1.6) upon 1 T applied magnetic field, which makes it suitable for sub-room temperature magnetic cooling material. (C) 2008 Elsevier B.V. All rights reserved.