Near-room-temperature magnetocaloric effect in electron-doped manganite probed by local atomic structure and critical exponent theory

Near-room-temperature and enhanced magnetocaloric properties are investigated for the chemical combustion synthesized electron-doped manganite La_1−xZr_xMnO₃ with x = 0.05, 0.10 and 0.15. The single-phase rhombohedral crystal structure is observed particularly for the La_0.90Zr_0.10MnO₃ (Zr10) system. Importantly, all the samples exhibit the paramagnetic-to-ferromagnetic (PM-to-FM) transition close to the room-temperature with the second-order phase transition. The analysis of the magnetic data in the critical region with different theoretical models such as 3D-Heisenberg, 3D-Ising, Mean-field, and Tri-critical mean-field suggested that the Zr10 sample exhibits the typical 3D-Heisenberg ferromagnetic characteristics. This indicated that the enhanced magnetic and magnetocaloric properties are governed by short-range exchange forces. Furthermore, the obtained data is also fitted with the Kouvel-Fisher method to obtain the transition-temperature, critical exponent β and it is found that the transition temperature and β values are totally consistent to that of the 3D-Heisenberg model. Significantly, the change in entropy |ΔS_m| at 5 T is calculated to be 4.04 J·kg⁻¹·K⁻¹ at 304 K in case of Zr10 sample indicating that it can be one of the potential material for the future magnetic refrigeration technology working at near room-temperature.