Magnetocaloric effect in La1–x Ca x MnO3 for x = 0.3, 0.35, and 0.4
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We present systematic studies of the magnetocaloric properties of the polycrystalline La1−x Ca x MnO3 system for x = 0.3, 0.35, and 0.4 near a second-order phase transition from a ferromagnetic to a paramagnetic state. The crystal structure of the studied manganites was shown to be in good agreement with previous reports. The value of the magnetocaloric effect has been determined from the measurement of magnetization as a function of temperature and external magnetic field. The maximum entropy change detected in La0.7Ca0.3MnO3 at a field of 2 T reaches 8 J/kg K which exceeds that of gadolinium. In all studied samples, the paramagnetic–ferromagnetic transition is very narrow but no hysteresis is observed and the transitions are identified as second-order ones. The phase transition in La0.7Ca0.3MnO3 appears to be almost of first-order.
KeywordsManganite Field Cool Magnetocaloric Effect Magnetic Entropy Change Zero Field Cool
This work was partly supported by the Ministry of Science and Higher Education of Poland Project PBZ-KBN-115/T08/2004. The authors thank W. Adamczuk for assistance during the experiment.