Half-metallic Ferromagnetism Properties Of Ternary Compound Zn_4-XY_XS₄（Y=V、Cr、Mn）: A First-principles Study

Spintronics is one of the latest subject related to microelectronics and magnetics, Ituses two degrees of freedom of the electronic charge and spin to the storage andprocessing of information. Compared with ordinary semiconductor electronic devices,spintronic devices has the advantages of non-volatile, low power consumption and highintegration. The key question is to find the spintronic materials with high spinpolarization and high Curie temperature at present. ZnS is the most wide band gapsemiconductor material in the Ⅱ-Ⅵ. The partial replacement of Zn atoms in ZnS bytransition metals （V, Cr, Mn） can get a half metallic material with high Curietemperature and high spin polarization （100%）. So, the diluted magneticsemiconductors of ZnS-based has important application value in the field of spintronics.In this paper, the energy band structure, density of states and magnetic propertiesof ternary compounds Zn_4-xY_xS₄（Y=V, Cr, Mn） are calculated by the first principlesmethod based on density functional theory （DFT）. Its half-metallic magnetic mechanismis researched, and impact of the half-metallic energy gap with different ratio of theconcentration that x=1and x=2, and the same concentration of different replacementposition are analysed. The main results are as follows:1) Zn_4-xY_xS₄with the different replacement concentration:（1） The two kinds of replacement （x=1, x=2） for V: Their half-metallic band gapare0.302eV and0.464eV respectively. The main reason is that spin-down sub-band bythe influence of Zn s orbital with the V concentration increases and move tohigh-energy side, resulting in its half-metallic energy gap to increase.（2） The two kinds of replacement （x=1, x=2） for Cr: Their half-metallic band gapare1.005eV to0.961eV respectively. The main reason is that with the dopingconcentration increases, the Cr atom interaction enhanced,3d band of Cr wider to theboth sides, which leading to spin-down sub-band energy position of conduction banddecline and its half-metallic energy gap smaller.（3） The two kinds of replacement （x=1, x=2） for Mn: The anti-ferromagnetictotal energy are lower than the ferromagnetic total energy, so the anti-ferromagneticstate is more stable ground state.2) The ternary compound Zn2Y2S4with the same concentration and the differentreplacement location: （1） For Zn₂V₂S₄and Zn₂Cr₂S₄, the half-metallic band gap of the same layerreplacement （b） are0.464eV and0.961eV respectively, and that of diagonal replacement（c） are0.253eV and0.758eV. The main reason that half-metallic band gap ofreplacement （b） is larger than that of replacement （c） is that the density of states peakless and spreading due to the Jahn-Teller effect in replacement of （c） leading tohalf-metallic band gap decreases. Therefore, this article speculated that V, Cr have planegathered.（2） For Zn₂Mn₂S₄, the ferromagnetic stabilization energy of diagonal replacementand the same layer replacement are all negative, which indicating that theanti-ferromagnetic state is more stable ground state. But the ferromagnetic stabilizationenergy of diagonal replacement is greater, which indicating that the systemferromagnetic stabilization energy gradually become larger and the system tends to aferromagnetic state with increasing of the distance of Mn-Mn atoms.The results of this paper is very consistent with the existing theoretical calculationsIn addition, we also got some new calculation results, and try to make a certaininterpretation. Although these also need to verify with further theoretical orexperimental, but it is some guiding significance for the study of the magneticsemiconductor.