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摘要
Atomically thin ferromagnetic (FM) films were recently prepared by mechanical exfoliation of bulk FM semiconductor Cr2Ge2Te6. They provide a platform to explore novel two-dimensional (2D) magnetic phenomena, and they offer exciting prospects for new technologies. By performing systematic ab initio density functional calculations, here we study two relativity-induced properties of these 2D materials (monolayer, bilayer, and trilayer as well as bulk), namely magnetic anisotropy energy (MAE) and magneto-optical (MO) effects. Competing contributions of both magnetocrystalline anisotropy energy (C-MAE) and magnetic dipolar anisotropy energy (D-MAE) to the MAE are computed. The calculated MAEs of these materials are large, being on the order of similar to 0.1 meV/Cr. Interestingly, we find that out-of-plane magnetic anisotropy is preferred in all the systems except the monolayer, where in-plane magnetization is favored because here the D-MAE is larger than the C-MAE. Crucially, this explains why long-range FM order was observed in all the few-layer Cr2Ge2Te6 except the monolayer because the out-of-plane magnetic anisotropy would open a spin-wave gap and thus suppress magnetic fluctuations so that long-range FM order could be stabilized at finite temperature. In the visible frequency range, large Kerr rotations up to similar to 2.2 degrees in these materials are predicted, and they are comparable to that observed in famous MO materials such as PtMnSb and Y3Fe5O12. Moreover, they are similar to 100 times larger than that of 3d transition metal monolayers deposited on Au surfaces. Faraday rotation angles in these 2D materials are also large, being up to similar to 120 degrees/mu m, and they are thus comparable to the best-known MO semiconductor Bi3Fe5O12. These findings thus suggest that with large MAE and MO effects, atomically thin Cr2Ge2Te6 films would have potential applications in novel magnetic, MO, and spintronic nanodevices.
- 出版日期2018-9-21
- 单位厦门大学
