Magnetic ground state of holmium nitride

Abstract

Rare-earth mononitrides such as HoN exhibit a wide range of useful properties leading to potential applications as magnetic semiconductors, spintronic half-metals, or magnetocaloric refrigerants in hydrogen liquefaction systems. First-principle calculations of electronic structures and related properties of such materials should correctly reproduce their magnetic moment. First, we identify the unusually high number of unoccupied electronic states which guarantees that the energy minimum identified is the global one. Second, we develop a method which allows the experimentally relevant magnetisation to constitute an energy minimum, emphasising the favourable distribution of the spins in an exceptionally large simulation cell. Third, we examine the dependence of selected HoN characteristics on the cell size and on the magnetisation. The results provide a theoretical insight into the spin structure of rare-earth nitrides and allow one to use the correct methodology of similar calculations of properties of strongly correlated materials.