Room-temperature magnetocaloric effect in La0.7Sr0.3Mn1-xM'xO3 (M'=Al, Ti)

TL;DR

This study investigates the magnetocaloric effect near room temperature in La0.7Sr0.3Mn1-xM'xO3 (M' = Al, Ti), showing how substitution affects entropy change, temperature span, and cooling power, relevant for magnetic refrigeration.

Contribution

It demonstrates how Al and Ti substitutions tune the ferromagnetic transition temperature and improve the magnetocaloric properties of manganites near room temperature.

Findings

Al substitution extends temperature span and enhances cooling power.

Ti substitution has minimal impact on magnetocaloric effect.

Magnetocaloric effect peaks at the ferromagnetic transition around 300 K.

Abstract

Magnetic entropy and adiabatic temperature changes in and above the room-temperature region has been measured for La0.7Sr0.3Mn1-xM'xO3 (M' = Al, Ti) by means of magnetization and heat capacity measurements in magnetic fields up to 6 T. The magnetocaloric effect becomes largest at the ferromagnetic ordering temperature Tc that is tuned to ~300 K by the substitution of Al or Ti for Mn. While the substitution of Al for Mn drastically reduces the entropy change, it extends considerably the working temperature span and improves the relative cooling power. The magnetocaloric effect seems to be only lightly affected by Ti substitution. Although manganites have been considered potential for magnetic refrigerants, the magnetocaloric effect in these materials is limited due to the existence of short-range ferromagnetic correlations above Tc.