Enhancement of magnetic refrigerant capacity in nanocrystalline LaMnO$_{3}$

Manganites are considered as potential magnetic refrigerants owing to their large magnetocaloric effect (MCE). However, the effective temperature span of large MCE ($\delta $T) is quite small in their bulk form resulting in small refrigerant capacity (RC). We have studied the magnetocaloric property of LaMnO$_{3 }$in its polycrystalline bulk and nanocrystaline form with particle size $\sim $50nm. MCE is quantified as the change in magnetic entropy (-$\Delta $S$_{M})$, which is calculated from the isothermal magnetization curves using Maxwell relation. The samples exhibit large -$\Delta $S$_{M}$ associated with their paramagnetic to ferromagnetic transition. Relative to the bulk sample, $\delta $T increases significantly in the nanocrystalline form giving rise to more than 63{\%} enhancement in RC. The calculated values of -$\Delta $S$_{M}$(RC) for bulk and nanocrystalline samples are $\sim $2.6J/KgK(173J/Kg) and 2.4J/KgK(282 J/Kg) respectively for magnetic field change of 50 kOe. From present study, it can be inferred that reduction of particle size to the nanoscale may be an effective way to increase $\delta $T and hence improve RC of a material.