Magnetocaloric effect in the doped perovskite manganese oxide La 0.7− xNd xSr 0.3MnO 3 ( x = 0.42, 0.56 and 0.7)

Abstract

The dependence of magnetization M (T) on the applied magnetic field H and temperature T was measured carefully, near the Curie temperature T C for the perovskite manganite samples La 0.7− x Nd x Sr 0.3MnO 3 ( x = 0.42, 0.56 and 0.7). By varying the Nd composition in these compounds, not only the magnetization but also the magnetic entropy change (Δ S M) have been enhanced. The Curie temperature has been analysed by two methods: a linear extrapolation of M (T) to zero magnetization, and the thermodynamic model. The experimental results indicate that T C decreases from 304 to 240 K with increasing Nd substitution independently of the method used to obtain T C. With increasing Nd concentration, a systematic increase in the values of magnetic entropy is observed (1.25 < |Δ S M| < 1.74) with H = 1.5 T. The large entropy change can be attributed to the fact that the ferromagnetic transition enhances the effect of the applied magnetic field greatly. It is suggested by the results that these materials can be used as the working material in an active magnetic regenerative refrigerator.