Effect of Cr substitution on magnetic and magnetic entropy change of La0.65Eu0.05Sr0.3Mn1−xCrxO3 (0.05≤x≤0.15) rhombohedral nanocrystalline near room temperature

• Nanocrystalline materials La0.65Eu0.05Sr0.3Mn1−xCrxO3 were obtained.
• The Cr substitution decreases the TC from 338 K for x=0.05–278 K for x=0.15.
• The relative cooling power of La0.65Eu0.05Sr0.3Mn1−xCrxO3 is nearly 54% of pure Gd.
• Arrott plot analyses was applied to study the order of the magnetic transition.
• La0.65Eu0.05Sr0.3Mn1−xCrxO3 samples show second order PM–FM transition at T=TC.

We have studied the effect of Cr substitution on magnetic and magnetocaloric properties in nanocrystalline La0.65Eu0.05Sr0.3Mn1−xCrxO3 (x=0.05, 0.1 and 0.15). The materials were prepared using the Pechini sol–gel method. All the studied samples were crystallized into a single phase rhombohedral structure with R−3C space group. Magnetic measurements indicate that the ferromagnetic double exchange interaction is weakened with increasing Cr concentration, resulting in a shift in TC from 338 K to 278 K as x   varied between 0.05 and 0.15. Detailed analyzes in the vicinity of the ferromagnetic (FM)–paramagnetic (PM) phase-transition temperature prove the samples undergoing a second-order phase transition. The magnetocaloric effect is calculated from the measurement of initial isothermal magnetization versus magnetic field at various temperatures. The maximum magnetic entropy change |ΔSMmax| is found to decrease with increasing of Cr content from 4.04 J/Kg K for x=0.05–0.78 J/KgK for x=0.15 upon 5 T applied field change.The relative cooling power (RCP) of La0.65Eu0.05Sr0.3Mn1−xCrxO3 series is nearly 54% of pure Gd, which will be an interesting system for application in room temperature refrigeration.