Effect of barium-deficiency on the structural, magnetic, and magnetocaloric properties of La0.65Ba0.35−x□xMnO3 (0 ≤ x ≤ 0.2) manganites

Magnetic, and magnetocaloric properties of La0.65Ba0.35−x□xMnO3 (0 ≤ x ≤ 0.2) have been investigated, where □ is a barium deficiency. Our samples were synthesized using the solid-state reaction method at high temperatures. Rietveld analysis show that the vacancy induces a structural transition from orthorhombic (Pbnm) for x = 0 to rhombohedral (R3¯c) for x ≥ 0.05. Magnetization measurements versus temperature under a magnetic applied field of 0.05 T indicate that all our samples undergo a paramagnetic ferromagnetic transition. The Curie temperature TC are found to be 325, 345, 332 and 288 K for x = 0, 0.05, 0.10 and 0.20, respectively. The maximum value of the relative cooling power RCP is obtained for x = 0.2 and is found to be 231 J/Kg under a magnetic field change of 5 T, which is around 60% of that observed in pure gadolinium. This compound is considered as a good material for magnetic refrigeration near room temperature.