Electronic Structure And Magnetism In Doped CoO And Ferromagnet/Mo S₂ Interfaces: A First-principles Study

Transition metal–oxide(TMO) nanomaterials have attracted much attention due to their intriguing magnetic properties and potential applications in the high-density storage devices and catalysis. Among them, anti-ferromagnetic Co O is one of the examples. Co O has a wurtzite(WZ) lattice structure, just like Zn O, instead of rock-salt-type lattice.Firstly, we study the case of Co O with one O vacancy and one Co vacancy. Ferromagnetic half-metallic characteristic in Co O with one Co vacancy appears. In order to further study the effect of Co vacancies on Co O, we calculate the Co O with two Co vacancies at different positions. Co O systems with two Co vacancies at the 9, 11 and 9, 16 positions are half-metallic, suggesting that these materials are the potential candidates in the field of spintronics devices. Besides, when the Co vacancies locate at 9 and 1 positions, the system shows a metallic characteristic.Secondly, we study the magnetism and electronic structure in Zn and Ti doped Co O. The Zn doped Co O is ferromagnetic insulators, but the magnetic moment of Co2+ ions is enhanced by the Zn incorporation. After introducing one Ti atom into Co O, the conductivity is enhanced. The Co O doped with Ti atoms on 9 and 11 positions shows a half-metallic character. Ti2Co14O16 systems with Ti at 9, 10 and 9, 16 and 1, 9 positions show the metallic character with a large spin polarization, which can make the conductivity of Co O systems enhanced.Finally, Mo S2 is one of the most stable layered transition metal dichalcogenides, and the structure of Mo S2 is formed by a graphene-like hexagonal arrangement of Mo and S atoms stacked together to give S-Mo-S sandwiches coordinated in a triangular prismatic fashion. we study the electronic structure and magnetism of the Fe(111)/Mo S2(001), Co(111)/Mo S2(001) and Fe3O4(111)/Mo S2(001) superlattices by first-principles calculations. We considered different structural models:(a) Fe-S(b-d) Co-S(e-g) Fe(A)-S(h-j) Fe(B)-S(k-m) O-S. The main finding can be summarized as follows: For models a-d, the semiconducting nature of Mo S2 disappeared and completed the spin injection in Mo S2. For models e-g, the semiconducting nature of Mo S2 is preserved and p-type doping. For models h-j, interfacial Fe(B)-S bonding is relatively weak. Mo S2 shows the metallic character and n-type conductivity. For models k-m, Forming ionic bonding across the interface of O and S. Mo S2 shows the metallic feature and p-type conductivity.