Probing the effects of Eu³⁺ on the structure, magnetic, and magnetocaloric effect of La_0.65Eu_xSr_0.35−xMnO₃

In this paper, the sol–gel (S–G) method was adopted to investigate the influence of doping different dopants of Eu³⁺ (x = 0.05, 0.10, 0.15, and 0.20) at the A-site on the structure, magnetism, and magnetocaloric effect (MCE) of La_0.65Eu_xSr_0.35−xMnO₃ (LE_xSMO). Through X-ray diffraction analysis (XRD), the LE_xSMO belongs to the rhombohedral structure with the R‾3c space group. By using the magnetic property test, the Curie temperatures (T_C) of the samples decrease progressively, and the T_C of x = 0.10 is near room temperature. The maximum magnetic entropy change \(\left( { - \Delta S_{M}^{Max} } \right)\) $\left(-\mathrm{\Delta }{S}_M^{\mathit{Max}}\right)$ reaches a maximum at x = 0.10( \(- \Delta S_{M}^{Max}\) $-\mathrm{\Delta }{S}_M^{\mathit{Max}}$  = 4.69 J·kg⁻¹·K⁻¹ at ΔH = 5 T) with increasing Eu³⁺ doping. Additionally, the analysis reveals that the second-order magnetic phase transition occurred around T_C with low hysteresis. It is a good illustration of Landau theory about the important contribution of electronic interaction and magnetoelastic coupling to the MCE mechanism of LE_xSMO near T_C.