Effect of structural defects on electronic and magnetic properties in pristine and Cr-doped HfS2 monolayer

Based on density functional theory, we investigate electronic and magnetic properties of pristine and Cr-doped monolayer HfS2 with vacancy defects. Nine possible vacancy defects types are considered. The results show that one hafnium (Hf) atom vacancy defect at monolayer HfS2 (V1Hf) will induces to 1.824μB magnetic moment and shows magnetic metallic property and the magnetic moments mainly comes from the nearest six S atom p orbitals. For two Hf atoms vacancy defects (V2Hf), the magnetic moment vanishes and the system shows semiconductor property. For the case of sulfur vacancy defects (VnS, n = 2, 3), all of these systems show magnetic metallic properties, and the total magnetic moment increases with increasing S vacancy defected atoms. When Hf+6S atoms are removed, the system is a magnetic metal with 0.501μB magnetic moment. In addition, we find 2V2S and 1V3S have the most stable structures when two and three S atoms are removed, respectively. When one Cr atom substitutes Hf atom in V1Hf, 2V2S and 1V3S systems (2Cr + V2S, 1Cr + V3S), 2.332μB, 2.806μB and 3.501μB magnetic moments are introduced, respectively. Cr atom is antiferromagnetic coupling to the nearest S atoms. These results show that S vacancy defects induce the charge redistribution of the nearest Hf atoms and appear the large charge polarization, thereby forming the larger local magnetic moment.