Electronic and magnetic properties of the double perovskites La2MnRuO6 and LaAMnFeO6 (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 La2MnNiO6, La2MnCoO6, and La2MnFeO6. While La2MnNiO6 and La2MnCoO6 are ferromagnets with near room-temperature T(C)s, a previous theoretical study of double-perovskite La2MnFeO6 revealed that this material is a ferrimagnet due to strong electronic interactions in Fe-d orbitals. Here we investigate the double-perovskites La2MnRuO6 and LaAMnFeO(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 La2MnFeO6 and lead to a ferromagnetic state. Our study reveals that while La2MnRuO6 is also a ferrimagnet, but with a higher net magnetic moment per formula than La2MnFeO6, doubly ordered LaAMnFeO(6) are ferromagnets. By mapping the total energy of the LaAMnFeO(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 TC of the three doped La2MnFeO6 materials with classical Monte Carlo calculations and predict that doubly ordered LaBaMnFeO6 and LaSrMnFeO6 could be suitable materials for room-temperature magnetic refrigeration.