Magnetic and magnetocaloric properties in second-order phase transition La1−xKxMnO3 and their composites.

In this work, we present a detailed study on the magnetic properties and the magnetocaloric effect (MCE) of La 1−x K x MnO 3 compounds with x =0.05–0.2. Our results pointed out that the Curie temperature ( T C ) could be controlled easily from 213 to 306 K by increasing K-doping concentration ( x ) from 0.05 to 0.2. In the paramagnetic region, the inverse of the susceptibility can be analyzed by using the Curie-Weiss law, χ ( T )= C /( T − θ ). The results have proved an existence of ferromagnetic clusters at temperatures above T C . Based on Banerjee's criteria, we also pointed out that the samples are the second-order phase transition materials. Their magnetic entropy change was calculated by using the Maxwell relation and a phenomenological model. Interestingly, the samples with x =0.1–0.2 exhibit a large MCE in a range of 282–306 K, which are suitable for room-temperature magnetic refrigeration applications. The composites obtained from single phase samples ( x =0.1–0.2) exhibit the high relative cooling power values in a wide temperature range. From the viewpoint of the refrigerant capacity, the composites formed out of La 1−x K x MnO 3 will become more useful for magnetic refrigeration applications around room-temperature. [ABSTRACT FROM AUTHOR]