摘要
We have investigated the magnetic and magnetocaloric properties of Lal.xCax.yAyrvlnO3 （A=K, Na and 0 -〈 x 〈 0.5） polycrystalline samples elaborated using several techniques （solid sate reaction at high temperatures, sol-gel method, SPS route ）. All our samples exhibit a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature Tc depends on the nature and the amount of the substituted element （x, y, Na, K）. From the magnetization measurements versus magnetic applied field M（H）, we have deduced the evolution of the magnetic entropy change ASM （T） and the relative cooling power RCP. Our studies show that our samples exhibit great magnetocaloric effect values near room temperature and consequently may be used in the magnetic refrigeration area. In order to enhance the magnetocaloric effect （MCE）, we have elaborated several composites based on the studied manganites and ferromagnetic oxides and studied its magnetocaloric properties. Our studies show that some composites with appropriate concentrations exhibit good RCP values near room temperature reaching that obtained in gadolinium Gd known as the prototype material for magnetic refrigeration around room temperature.
