Enhanced relative cooling power in Ga-doped La-0.7(Sr,Ca)(0.3)MnO3 with ferromagnetic-like canted state

摘要

The effect of diamagnetic gallium "Ga" substitution on the microstructural, magnetic and magnetocaloric properties in perovskite, La-0.7(Sr,Ca)(0.3)MnO3, has been investigated. The La-0.7(Sr,Ca)(0.3)Mn1-xGaxO3 compounds undergo a rhombohedral-to-orthorhombic structural transition at x = 0.15. The partial substitution of Mn by Ga leads to a monotonic decrease in the Curie temperature (T-C) of the compounds from 335 K for x = 0.00 to 138 K for x = 0.20. The ferromagnetic transition was broadened when introducing Ga content. Magnetic entropy (Delta S-M) curves show a peak around the ferromagnetic-paramagnetic Curie temperature, which decreases from 5.16 J kg(-1) K-1 for x = 0.00 to 2.08 J kg(-1) K-1 for x = 0.20, with an applied magnetic field of mu(0)Delta H = 5 T. Because of the relatively easy possibility of tuning the Curie temperature and the interesting values of relative cooling power (RCP), these compounds can be considered as suitable candidates for room- temperature magnetic refrigeration. Moreover, our results suggest that the magnetocaloric effect (MCE) is an effective analysis to gain a basic understanding about the magnetic ordering.