First-principles prediction of magnetic salts: Case study of NaCl bulk and (0 0 1) surface doped with light non-metallic 2p-block elements

Abstract

Based on density functional calculations, we studied the structural, electronic, and magnetic properties of sodium chloride bulk and (001) surface doped with the light non-metallic elements boron, carbon, nitrogen, and oxygen. The results indicated that doping such an isolated foreign atom can produce considerable spin polarization, mainly due to highly localized and partially filled 2p states of the dopants. From simple GGA computation, all these diluted magnetic chlorides exhibit nearly half-metallic characteristic with weak conductivity, and thereby they could be used as spin filter materials for improving spin-specific magnetic tunnel junctions. Especially, substitution onto the surface removes the degeneration of 2p impurity states, leading to anisotropic spin and electron atmosphere with specific orientation. The differences between bulk doping and surface doping were further explained by spin-resolved energy spectrums. In addition, compared with standard GGA approach, applied Ueff of 2p orbitals of C, N, and O atoms can correct the error and improve the description of the electronic structures and magnetic properties in some extent. N and O-doped NaCl bulks transform from approximate half metals to magnetic semiconductors, owning to the enhancement of electronic localization and correlation. And the total magnetic moment increases from 1 μB to 3 μB for C-doped NaCl (001), accompanying with a transformation from intermediate-spin state to high-spin state. In particular, O-substituted system is energetically more favorable than other doped systems, i.e., the negative value of the predicted formation energy, demonstrating that O-doped NaCl should be a candidate material for potential spintronic applications.