LAUSR

Abstract The magnetic Mn 3+ ions in La 0.7 Ca 0.3 MnO 3 are partially replaced by nonmagnetic Zn 2+ ions to form La 0.7 Ca 0.3 Mn 1−x Zn x O 3 compounds ( x =0.0, 0.06, 0.08, and 0.1), and their magnetic and magnetocaloric properties are investigated. The Curie temperature decreases drastically from 245 to 70 K as x increases from 0 to 0.1. An analysis using the Banerjee's criterion of the experimental results for magnetization as a function of temperature and magnetic field indicates that the first-to-second order magnetic phase transformation occurs at a threshold composition of x =0.06, which is further supported by the universal curves of the normalized entropy change versus reduced temperature. The maximum magnetic entropy change measured at a magnetic field span of 50 kOe, which occurs near the Curie temperature, decreases from 10.30 to 2.15 J/kg K with the increase of x from 0.0 to 0.1. However, the relative cooling power, an important parameter for practical applications, shows a maximum value of 404 J/kg at x =0.08, which is 1.5 times greater than that observed for the undoped sample.