Electronic and magnetic properties of the double perovskites La 2 MnRuO 6 and LaA MnFeO 6 ( A = Ba , Sr , Ca ) and their potential for magnetic refrigeration

Magnetic refrigeration at room-temperature is a technology that could potentially be more environmentally friendly, efficient, and affordable than traditional refrigeration. The search for suitable materials for magnetocaloric refrigeration led to the study of double-perovskites La 2 MnNiO 6 , La 2 MnCoO 6 , and La 2 MnFeO 6 . While La 2 MnNiO 6 and La 2 MnCoO 6 are ferromagnets with near room-temperature T C s , a previous theoretical study of double-perovskite La 2 MnFeO 6 revealed that this material is a ferrimagnet due to strong electronic interactions in Fe − d orbitals. Here we investigate the double-perovskites La 2 MnRuO 6 and La A MnFeO 6 ( A = Ba, Ca, and Sr) with density functional theory (DFT) as materials that can counteract the effects the strong repulsion present in the in Fe − d shells of La 2 MnFeO 6 and lead to a ferromagnetic state. Our study reveals that while La 2 MnRuO 6 is also a ferrimagnet, but with a higher net magnetic moment per formula than La 2 MnFeO 6 , doubly ordered La A MnFeO 6 are ferromagnets. By mapping the total energy of the La A MnFeO 6 compounds obtained from DFT calculations to the Ising model, we also calculate their magnetic exchange couplings. This allows us to estimate the trend in T C of the three doped La 2 MnFeO 6 materials with classical Monte Carlo calculations and predict that doubly ordered LaBaMnFeO 6 and LaSrMnFeO 6 could be suitable materials for room-temperature magnetic refrigeration.