Magnetocaloric effect in $La_{1-x}Na_{x}SrMn_{2}O_{5+\delta}$ (with x = 0.1 , 0.2 and 0.3)

Abstract.

The present paper is aimed to analyze the effects of sodium substitution on the magnetic entropy change between $La_{0.9}Na_{0.1}SrMn_{2}O_{5+\delta}$ and $La_{0.8}Na_{0.2}SrMn_{2}O_{5+\delta}$ polycrystalline samples. Evaluation of the potential magnetocaloric effects is sought through identifying the magnetic entropy change $\Delta S_{M}$, which was basically determined from the magnetic field dependences of magnetization at different temperatures $M(H,T)$ near $T_{C}$. Interestingly, the substitution of a small amount of Na in $La_{1-x}Na_{x}SrMn_{2}O_{5+\delta}$ nanocrystalline samples (with $x=0.1$, 0.2 and 0.3) reduced the maximum magnetic entropy $\vert\Delta S_{Max}^{M}\vert$ from 2.2 J kg^-1K^-1 (for $x=0.1$ to 0.8 Jkg^-1K^-1 (for $x=0.3$ for a field change $\Delta H=5$ T. The relative cooling power (RCP) decreases with increasing Na content reaching 53.13J kg^-1 for $x=0.3$ ($\Delta H=5$ T), respectively.