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 I4/mmm tetragonal bilayered perovskites phase for x ≤ 0.8, while they are mixture of a main orthorhombic ABO3-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.