Structural, magnetic and magnetocaloric properties of the lanthanum deficient in La0.8Ca0.2-x▭xMnO3 (x=0-0.20) manganites oxides

The La0.8Ca0.2-x rectangle xMnO3, (x = 0-0.20) compounds were prepared by the solid-state reaction. X-ray diffraction (XRD) and magnetic measurements were used to investigate the calcium-vacancy effect on the physical properties. The XRD data have been analyzed by Rietveld refinement technique. Samples with x = 0, 0.05 and 0.10 are found to be single phase and crystallize in orthorhombic symmetry with Pnma space group. Moreover, for x = 0.15 and 0.20 samples, the refinement has revealed the coexistence of both Pnma orthorhombic and R (3) over barc rhombohedral phases. The magnetic study has showed that the magnetization exhibits maximum at x = 0.15 and minimum at x = 0.2. Such behavior was interpreted in terms of orthorhombic distortion contribution, which is related to the orthorhombic structure, leading to magnetization decrease. In addition, maximum magnetic entropy change (Delta S-M) for x = 0 sample was found to reach similar to 4.1 J/kgK under an applied magnetic field of 5 T, which is very sufficient for potential application in magnetic refrigeration. For the same applied magnetic field (mu H-0= 5 T), the Relative Cooling Power (RCP) values are found to vary between 270 and 300 J/kg. As consequence, the La0.8Ca0.2-x rectangle xMnO3 compounds can be used as a composite for magnetic refrigeration in the [175-183] K temperature range. (C) 2011 Elsevier B.V. All rights reserved.