The impact of disorder on magnetocaloric properties in Ti-doped manganites of La0.7Sr0.25Na0.05Mn(1−x)TixO3 (0≤x≤0.2)

This work reports the effect of Ti doping on the structural, magnetic and magnetocaloric properties of La0.7Sr0.25Na0.05Mn(1−x)TixO3 (LSNMTix) (0≤x≤0.2) manganese perovskite prepared by the conventional solid-state reaction. Rietvelds' refinement result of X-ray power diffraction using the FullProf refinement program indicates that these compounds have a rhombohedrally distorted structure with a space group R3̅c. Magnetization as a function of temperature shows that all samples exhibit a paramagnetic (PM) - ferromagnetic (FM) phase transition at the Curie temperature TC which decreases from 363 K to 125 K for x=0-0.2, respectively. The magnetic entropy change (ΔSM) deduced from the measured magnetization M (µ0H) data using Maxwell relation, strongly depends on the Ti content. The maximum value of magnetic entropy change has been observed in our samples with a peak centered around their respective TC decrease from 4.34 J kg−1 K−1 to 2.03 J kg−1 K−1 for x=0 and x=0.2 at µ0H=5 T respectively. In addition, the relative cooling power (RCP) values inferred from the |ΔSM| vs. T peak broadening, vary slightly with the titanium content reaching values between 298 and 273 J kg−1 for an applied magnetic field of 5 T when x increases from 0 to 0.2. Technically, these results suggest that the material can be considered as suitable candidate as working substance in magnetic refrigeration.