Cr₂XTe₄ (X = Si, Ge) monolayers: a new type of two-dimensional high-T _C Ising ferromagnetic semiconductors with a large magnetic anisotropy

Abstract

Two-dimensional (2D) ferromagnetic semiconductor (FMS) provides the ideal platform for the development of quantum information technology in nanoscale devices. However, most of them suffer from low Curie temperature and small magnetic anisotropic energy (MAE), severely limiting their practical application. In this work, by using first-principles calculations, we predicted two stable 2D materials, namely, Cr2SiTe4 and Cr2GeTe4 monolayers. Interestingly, both of them are intrinsic direct band gap FMSs (∼1 eV) with a large magnetization (8 µ B f.u.−1) and sizable MAE (∼500 μ eV Cr−1). Monte Carlo simulations based on Heisenberg model suggest markedly high Curie temperatures of these monolayers (∼200 K). Besides, their high mechanical, dynamical, and thermal stabilities are further verified by elastic constants, phonon dispersion calculations, and ab initio molecular dynamics simulations. The outstanding attributes render Cr2XTe4 (X = Si, Ge) monolayers broadening the candidates of 2D FMS for a wide range of applications.

Ferromagnetic and half-metallic phase transition by doping in a one-dimensional narrow-bandgap W6PCl17 semiconductor

“…2 This broke the stranglehold of the Mermin-Wagner theorem, 3 which indicated that long-range magnetic ordering was strictly forbidden in low-dimensional materials. For lowdimensional materials, magnetism can be regulated by various measures, such as an external electric field, 4,5 strain and stress engineering, [6][7][8] edge modification, 9 surface adsorption, [10][11][12] transition-metal atom doping, [13][14][15] defect engineering 16,17 and carrier doping. [18][19][20] In fact, carrier doping is always the most appropriate method to induce itinerant ferromagnetism, con-forming to Stoner's criterion.…”

Intrinsic magnetism with high critical temperatures and piezoelectricity in 2D transition metal tetraborides

“…), the valence band maximum (VBM) and conduction band minimum (CBM) are contributed by B-p z /Co-d xy and B-p z /Co-d xz electrons (Figure 3G).It is demonstrated that the magnetocrystalline anisotropy can break the symmetry in 2D magnetic materials, which can effectively stabilize the long-range magnetic ordering[49][50][51]. Magnetic anisotropic energy (MAE) value is defined as the largest energy between magnetization of the magnetic easy axis and hard axis, which can be used to weight the spin flipping difficulty.…”

Origin and regulation of triaxial magnetic anisotropy in the ferromagnetic semiconductor CrSBr monolayer

“…[6][7][8][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Further analysis shows that magnetic anisotropy (MA) is the prerequisite and foundation to verify whether a 2D material exhibits a magnetically ordered phase above zero temperature, [28][29][30] and the 2D FM order can be stabilized by the magnon excitation gap caused by uniaxial magnetic anisotropy. [31][32][33] MA, which can be scaled by the magnetic anisotropy energy (MAE), is mainly determined by two factors; one is the magnetocrystalline anisotropy resulting from the spin-orbit coupling interaction (SOC-MAE) and the other is the shape anisotropy caused by the dipole-dipole interaction (shape-MAE). 34 Compared with the SOC-MAE, the shape-MAE is often relatively weak and of less concern.…”