Nguyen Huy Sinh, Do Hong Minh, Vu Thanh Mai

Magnetic properties of La_0.54Ca_0.32MnO_3-δ compound have been investigated from 4 K to 320 K. It is found that the Curie temperature is as high as 300 K, which is significantly higher than that of the La_1-xCa_xMnO_3-δ system. The ordering magnetic transition and semiconductor-metal transition have been observed at T_C on the magnetization susceptibility and resistivity versus temperature on the magnetization susceptibility resistivity versus temperature curves. The magnetic entropy change reaches a maximum value of - ΔS_M = 5.5 J/kg.K at the Curie temperature upon a 5 T magnetic field variation. Saturation magnetic moment value of σ_s = 2.99μ_B/fu at 5 K has been obtained from the magnetization data. Values of 0.0230 and 0.441 have been determined for the oxygen deficiency δ and the ratio of Mn³⁺/Mn⁴⁺, respectively. From obtained results it is suggested that this compound may be useful for application as a working substance in magnetic refrigeration at room temperature.

Advances in Natural Sciences Vol.4, No.4 (2003) (339-346)