What Can ABACUS Do Too? | Explore the Anomaly of Spin Polarization in CrTe2 Thin Films by Combining with TB2J Software

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Recently, teams led by Professor Yongbing Xu from Nanjing University, Professor Lin Miao from Southeast University, and Professor Lixin He from the Hefei Comprehensive National Science Center Institute of Artificial Intelligence collaborated. By combining Mott polarization measurement technology and first-principles calculations, they found that the two-dimensional vdw magnet CrTe2 has significantly enhanced spin polarization in its ultrathin limit. Especially at a thickness of 3 layers, the spin polarization rate reaches 23.4%. The researchers used the domestic open-source density functional theory software ABACUS (Atomic Abacus) + TB2J software to calculate in detail the magnetic anisotropy energy and interlayer exchange interaction of CrTe2 thin films at different thicknesses, highlighting the relevance of perpendicular magnetic anisotropy, interlayer interaction, and electron itinerant behavior to spin polarization at different film thicknesses. The research results "Substantially Enhanced Spin Polarization in Epitaxial CrTe2 Quantum Films" were published in the Advanced materials journal.

Paper link: https://onlinelibrary.wiley.com/doi/10.1002/adma.202411137

Research Results

The experimental team used X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements to study the local electronic structure and magnetic ground state of CrTe2 thin films. They also combined angle-resolved photoemission spectroscopy and spin-resolved photoemission spectroscopy to systematically study the electronic band structure and spin texture of CrTe2 thin films. Using Mott polarization measurement technology, they directly detected the spin degrees of freedom in CrTe2 thin films and discovered for the first time that there is significantly enhanced spin polarization in CrTe2 thin films. Subsequently, the theoretical calculation team combined the first-principles and Green's function methods and applied ABACUS + TB2J software to calculate and analyze the changes in magnetic anisotropy energy and interlayer exchange interaction at different layer thicknesses. They found that the magnetic anisotropy energy of CrTe2 thin films increases as the film thickness decreases, which is consistent with the experimental results. The interlayer exchange interaction increases as the film thickness increases, indicating that the interlayer interaction is crucial for maintaining the magnetic order. The experimental and theoretical results not only confirm that CrTe2 thin films are a promising two-dimensional ferromagnetic material but also provide an important experimental and theoretical basis for designing new spintronic devices.

Figure: (a) Evolution of the spin band calculated along the M-Γ-K direction. (b) Density of states (DOS) of CrTe2. (c) Experimental band dispersion along the M-Γ-M high-symmetry direction. (d) Experimental photoemission spectra of films with different thicknesses along the M-Γ-M direction. (e) Hysteresis loops of CrTe2 films with different thicknesses. (f) Thickness-dependent spin polarization of CrTe2, Mr, Ku. (g) MAE of CrTe2 calculated by DFT at different thicknesses. (h) Average interlayer exchange interaction Jave of CrTe2 calculated by DFT at different thicknesses.

Acknowledgments

Associate Professor Xiaoqian Zhang from Southeast University, Postdoctoral Fellow Qiangsheng Lu from Oak Ridge National Laboratory, and Associate Researcher Zhenxiong Shen from the Hefei Comprehensive National Science Center Institute of Artificial Intelligence are the co-first authors of this paper. Professor Lin Miao from Southeast University, Professor Yongbing Xu and Professor Liang He from Nanjing University, Professor Guang Bian from the University of Missouri, and Professor Chang Liu from Southern University of Science and Technology are the co-corresponding authors. This achievement was supported by the National Key R & D Program and the National Natural Science Foundation of China.

ABACUS official website:
https://abacus.deepmodeling.com

TB2J official doc:
https://tb2j.readthedocs.io/en/latest/