Magnetocaloric Properties of A-Site-Doped La2NiMnO6 for Environmentally Friendly Refrigeration

La2NiMnO6 double perovskite material that simultaneously exhibits both electric and magnetic ordering is used in energy-efficient electronic applications due to its lower power dissipation. The magnetic and electric ordering of Ni and Mn depend on the site occupancy and exchange mechanism driven by the anions, making La2NiMnO6 a widely explored material for such studies. The magnetocaloric properties of A-site-doped (Sr2+, Gd3+) double perovskite La2NiMnO6 have been investigated experimentally. The synthesized samples showed Pbnm orthorhombic symmetry with P21/n configuration. The Curie temperature (TC) of La2NiMnO6 (LMN) increased from 277 K to 284 K upon Gd doping due to strong exchange interactions and long-range ordering of Ni2+/Mn4+. Meanwhile, the Tc of LMN was observed to be 268 K upon Sr2+ doping, suggesting the possibility of antiferromagnetic ordering. Sr2+-doped (hole-doped) LMN showed lower Tc, magnetic entropy, and relative cooling power (RCP), which may be due to the increase in antisite disorder and exchange bias effect. The chemical stability, tunable transition temperature around room temperature with good control over entropy, wider operating temperature range, and high RCP at lower applied magnetic field make LMN and A-site-doped LMN potential refrigerant materials for use in energy-efficient room-temperature magnetic cooling systems.