First Principles Study On The Electronic And Magnetic Structures Of The3d-transition-metal Pnictides

With the development of science and technology, because spintronics materialshave the two degrees of freedom of electric charge and spin and at the same time thetwo degrees of freedom have been used for the storage and processing of information inthe solid, so it has been attracted more and more attention. Now computer chips havereached submicron scale, and the size of the device will be too small to tens ofnanometers and even a few nanometers in order to improve the information storage andprocessing capacity, so it requires that the related materials on the nanometer scale stillhave high spin polarization and excellent structural stability and performance stability.Most of the present study is dilute magnetic semiconductor materials in spintronics materials,although its spin polarization can be as high as100%, but diluted magnetic semiconductormagnetic atoms are too little to cause reduction in performance or even disappearancewhen its scale is reduced to the nanometer scale, so it’s not ideal for preparation ofnano-scale electronic devices. This raises a high demand on related materials, andrequires that it can still maintain the orientation of spin coherence and excellentstructure and stability when the size of the device is down to the nanometer scale. Whilethe transition-metal-phosphides of zinc-blende phase have a wider band gap ofnon-metallic bands, and are with enough high Curie temperature and nearly100%spinpolarization at the same time.Because the vast majority of them are half-metallicferromagnets and compatible with the semiconductor and their performance isobviously better than that of the diluted magnetic semiconductor, so it is considered tobe the ideal components of nano-scale spintronic devices in the future.In this paper, theoretic investigation on the electronic structures of zinc-blend of3d-transition-mental pnictides XY (X=V、Cr、Mn，Y=P、As、Sb) were carried out bythe first-principles plane-wave pseudopotential (PWP) method within the generalizedgradient approximation (GGA) based on the density functional theory (DFT). We cometo the following major conclusions:1. The3d-transition-mental pnictides XY (X=V、Cr、Mn，Y=P、As、Sb) ofzinc-blend except MnP, MnAs are half-metallic ferromagnets. The source ofhalf-metallic ferromagnetic is that t2gof3d of transition metal (V, Cr) and np ofphosphorus (P, As, Sb) hybrid and the hybrid states split and form the bonding andantibonding state。 2. The analysis of PDOS shows that the contribution of s-state to the total totalstate densities at the Fermi level is almost zero; s-state has a small amount of thecontribution to the total total state densities; the major contribution to the total total statedensities at the Fermi level come from d-state, which is mainly from V, Cr, Mn of thetransition-metal atoms3. The total magnetic moments are2.00μBand the magnetic configuration of V is3d2for V-phosphides; the total magnetic moments are3.00μBand the magneticconfiguration of Cr is3d3for Cr-phosphides. The results show that the ferromagneticcoupling in Cr-phosphides is stronger than that in V-phosphides. But the total magneticmoments of MnP and MnAs are2.42μB,3.70μB, respectively and the total magneticmoments are not an integer multiple of Bohr magneton; so MnP and MnAs arehalf–metal ferromagnets approximately and are not half–metal ferromagnets really.The above results are accord with the existing theoretical calculation results, inaddition we also obtained some related rules and make the explanation, and thisprovides a valuable reference for further research.