Magnetic entropy change in polycrystalline La1−xKxMnO3 perovskites

Polycrystalline samples of potassium doped lanthanum manganites having nanometric crystallite size have been synthesized by pyrophoric method. The Curie temperature (TC) of the prepared samples is found to be strongly dependent on K content and spans between 260 and 309 K. Close to TC, large change in magnetic entropy has been observed in all the samples. The maximum magnetic entropy change observed for samples with different concentration of K, exhibits a linear dependence with the applied magnetic field. Adiabatic temperature change at TC at 1 T also increases with K doping and attains a maximum of 2.1 K for La0.85K0.15MnO3. Estimated relative cooling power of La1−xKxMnO3 compounds is nearly one-third of pure Gd. In addition to the tuneability of TC between 260 and 310 K, higher chemical stability, lower eddy current heating and inexpensive preparation technique; the magnetic entropy change in La0.85K0.15MnO3 compound at 1 T magnetic field is found to be 3.00 J/kg K and is ∼89% to that known for the prototype magnetic refrigerant (pure Gd). Our result on magnetocaloric properties suggests that La1−xKxMnO3 compounds are attractive as a possible refrigerant for near room temperature magnetic refrigeration.