Enhancement of magnetocaloric effect by partial substitution of Bi in La_0.60Dy_0.10Sr_0.30Mn_(1−x)Bi_xO₃ manganites (x = 0, 0.01, 0.03, and 0.10)

In this study, the effects of Bi substitution for Mn on the magnetic and magnetocaloric properties of La_0.60Dy_0.10Sr_0.30Mn_(1−x)Bi_xO₃ manganites (x = 0, 0.01, 0.03, and 0.10) synthesized using the sol–gel method ​​were investigated. The samples x = 0, 0.01, and 0.03 had been indexed in an orthorhombic structure (space group Pnma), while sample x = 0.10 had been indexed in a hexagonal structure (space group R3c). The thermomagnetic measurements showed an increase in the Curie temperature (T_C) with increasing Bi content, as well as an increase in magnetization at low temperatures. The T_C values were determined as 322, 318, 327, and 360 K for x = 0, 0.01, 0.03, and 0.10 samples, respectively. Maximum magnetic entropy change ( \(-\Delta {S}_{M}^{max}\) $-\mathrm{\Delta }{S}_M^{\mathit{max}}$ ) values ​​obtained from isothermal magnetization measurements showed an increase with the amount of Bi. The \(-\Delta {S}_{M}^{max}\) $-\mathrm{\Delta }{S}_M^{\mathit{max}}$ value of 3.80 Jkg⁻¹K⁻¹ at 5 T for the x = 0 sample increased to 4.12 Jkg⁻¹K⁻¹ for the x = 0.10 sample with the highest Bi content. From the Arrott curves, it was observed that all samples exhibited a second-order magnetic phase transition. The obtained values of relative cooling power (RCP), which is an important factor in determining the performance of cooling material, are in the range of 282, 262, 251, and 232 Jkg⁻¹ for x = 0, 0.01, 0.03, and 0.10, respectively.