Bulk and surface sp half-metallic ferromagnetism in alkali metal pnictides with rocksaltstructure: a first-principles calculation

Abstract

Recently, sp half-metallic ferromagnetism in alkali metal/alkaline earth pnictides(I/II–V) with zinc blende structure was predicted by first-principles calculations(Sieberer et al 2006 Phys. Rev. B 73 024404). To search for half-metallicferromagnets with a more stable structure in alkali metal pnictides MX (M = Li, Na,K; X = N, P, As), we apply here first-principles all-electron and pseudopotential-method-baseddensity functional theory to investigate the electronic and magnetic propertiesof these compounds with rocksalt structure. Five rocksalt compounds arefound to be half-metallic ferromagnets with a magnetic moment of 2.00μB/f.u., and they are more stable energetically than the ones with zinc blende structure, whichmakes them more promising candidates for the possible growth of half-metallic films orultrathin films on suitable semiconductor substrates. Furthermore, we show that bothlithium- and nitrogen-terminated (111) surfaces of rocksalt lithium nitride retain the bulkhalf-metallic characteristic, and the surface atomic magnetic moments are enhancedcompared to the bulk values.