Striped antiferromagnetism and electronic structures of SrFeAsF and their implications

We investigate structural, magnetic, and electronic properties of SrFeAsF as a new parent for superconductors using state-of-the-art density-functional theory method. Calculated results show that striped antiferromagnetic order is the magnetic ground state in the Fe layer and interlayer magnetic interaction is tiny. Calculated As and Sr positions are in agreement with experiment. There are only two uniaxially-dispersed bands near the Fermi level. The valent charge is mainly in the Fe and F layers, and the magnetic moment is confined to the Fe atoms. Inter-Fe-spin couplings is due to superexchange through As atoms. These are useful to understanding the SrFeAsF and should have helpful implications to doped samples.

Half-metallic ferrimagnet formed by substituting Fe for Mn in semiconductor MnTe

A ternary ferrimagnetic half-metal, constructed through substituting 25% Fe for Mn in zincblende semiconductor MnTe, is predicted in terms of accurate first-principles calculations. It has a large half-metallic (HM) gap of 0.54eV and its ferrimagnetic order is very stable against other magnetic fluctuations. The HM ferrimagnetism is formed because the complete moment compensation in the antiferromagnetic MnTe is replaced by an uncomplete one in the Fe-substituted MnTe. This should make a novel approach to new HM materials. The half-metal could be fabricated because Fe has good affinity with Mn, and useful for spintronics.

Nitrogen defects and ferromagnetism of Cr-doped AlN diluted magnetic semiconductor from first principles

High Curie temperature of 900 K has been reported in Cr-doped AlN diluted magnetic semiconductors prepared by various methods, which is exciting for spintronic applications. It is believed that N defects play important roles in achieving the high temperature ferromagnetism in good samples. Motivated by these experimental advances, we use a full-potential density-functional-theory method and supercell approach to investigate N defects and their effects on ferromagnetism of (Al,Cr)N with N vacancies (V_N). Calculated results are in agreement with experimental observations and facts of real Cr-doped AlN samples and their synthesis. Our first-principles results are useful to elucidating the mechanism for the ferromagnetism and exploring high-performance Cr-doped AlN diluted magnetic semiconductors.