Large magnetocaloric effect near room temperature in 𝐋𝐚_0.67(𝐒𝐫,𝐊/𝐏𝐛)_0.33𝐌𝐧𝐎_3 manganite nanomaterials

The magnetic and magnetocaloric properties of La_0.67Sr_0.33MnO_3 ( LSMO ), La_0.67Sr_0.23K_0.10MnO_3 (LSKMO), and La_0.67Sr_0.23Pb_0.10MnO_3 (LSPMO) manganite nanomaterials were investigated. The superparamagnetic behavior of these nanomaterials was analyzed using the log-normal weighted Langevin function. Large change in magnetic entropy ( Δ S_M ) and relative cooling power (RCP) were observed near the Curie temperature, T_C , for all samples. The maximum change in entropy ( -Δ S_M^max ) is found to be 5.0, 5.3, and 6.2 J kg^-1K^-1 under 7 T magnetic field for LSMO , LSKMO, and LSPMO samples, respectively, whereas the corresponding RCP values are 400, 440, and 325 J kg^-1 . The isothermal magnetization data were analyzed thoroughly, using Arrott plots according to Banerjee’s criterion. Moreover, the critical exponents ( β , γ and δ ) were calculated using the modified Arrott plot. The Widom scaling relation was studied to confirm the dependability of these critical exponents. The magnetocaloric effect was also analyzed by considering the Landau theory. Our findings indicate that these samples can have promising applications for magnetic refrigeration.