Studies on magnetic and magnetocaloric properties of double perovskite La_2 NiMnO_6 system

The present work aims to make an estimate of the adiabatic temperature change ( Δ T_ add ) parameter due to the magnetocaloric effect (MCE), for the rare-earth (RE)-based double perovskite La_2 NiMnO_6 system. Isothermal magnetization ( M versus H ) measurements are carried out on the La_2 NiMnO_6 sample, at temperatures around the ferromagnetic phase transition temperature ( T_C ). The experimental magnetization data of La_2 NiMnO_6 are analyzed by using the Weiss mean-field model theory (MFT) and Landau theory of phase transitions. The magnetocaloric properties such as the isothermal magnetic entropy change ( Δ S_M ), refrigerant capacity (RC) and the adiabatic temperature change ( Δ T_ add ) are evaluated using the experimental and numerically computed/simulated data. For the estimation of the adiabatic temperature change, the heat capacity data of La_2 NiMnO_6 system are generated using the mean-field model data and the reported Debye temperature ( Θ _D ) value of La_2 NiMnO_6 . Additionally, Monte Carlo simulations are performed for the La_2 NiMnO_6 system, using Ising model Hamiltonian. The magnetocaloric properties are also extracted from the Monte Carlo simulations data. The La_2 NiMnO_6 shows a maximum adiabatic temperature change of around 2.3 K for the magnetic field change from zero to 70 kOe.