Microscopic origin of the magnetic easy-axis switching in Fe3GaTe2 under pressure

TL;DR

Fe3GaTe2 exhibits a pressure-driven spin reorientation from out-of-plane to in-plane around a critical pressure $P_c \approx 10$ GPa. Using first-principles DFT, the study links this transition to anisotropic c-axis compression that broadens bands and causes opposite shifts of spin-up and spin-down states near the Fermi level, reducing magnetization. The transition is dominated by site-resolved SOC changes on FeI and Te, with FeII remaining insufficient to counterbalance the in-plane tendency. These results show how hydrostatic pressure can tune magnetocrystalline anisotropy in layered ferromagnets, offering a route to tailor spin orientation for spintronic devices.

Abstract

The two-dimensional layered ferromagnet Fe3GaTe2, composed of a Te-FeI-FeII/Ga-FeI-Te stacking sequence, hosts two inequivalent Fe sites and exhibits a high Curie temperature and strong out-of-plane magneticanisotropy, making it a promising platform for spintronic applications. Recent experiments have observed a pressure-induced switching of the magnetic easy axis from out-of-plane to in-plane near 10 GPa, though its microscopic origin remains unclear. Here, we employ first-principles calculations to investigate the pressure dependence of the magnetocrystalline anisotropy energy in Fe3GaTe2. Our results reveal a clear easy-axis switching at a critical pressure of approximately 10 GPa, accompanied by a sharp decrease in the magnetic moments arising from FeI and FeII atoms. As pressure increases, spin-up and spin-down bands broaden and shift oppositely due to band dispersion effects, leading to a reduction in net magnetization. Simultaneously, the SOC contribution from FeI, which initially favors an out-of-plane easy axis, diminishes and ultimately changes sign, thereby promoting in-plane anisotropy. The SOC contribution from the outer-layer Te atoms also decreases steadily with pressure, although it retains its original sign; this additional reduction further reinforces the in-plane magnetic easy axis. In contrast, FeII atoms continue to favor an out-of-plane orientation, but their contribution is insufficient to counterbalance the dominant in-plane preference at high pressure. These findings elucidate the origin of magnetic easy-axis switching in Fe3GaTe2 and provide insights for tuning magnetic anisotropy in layered materials for spintronic applications.

Figures (7)

• Figure 1: Optimized crystal structure of Fe$_3$GaTe$_2$: (a) Perspective view of the layered structure; (b) top and side views of the unit cell, together with the first Brillouin zone of the hexagonal lattice; (c) calculated pressure dependence of the lattice parameters $a$, $b$, and $c$, as well as the interlayer spacing $d_{\text{int}}$. The lattice parameters are $a$ = ($a$, 0, 0), $b$ = ($-b$ sin(30$^{\circ}$), $b$ cos(30$^{\circ}$), 0), and $c$ = (0, 0, $c$) in the $x$, $y$, $z$ coordinate system.
• Figure 2: (a) Calculated spin-polarized band structure of Fe$_3$GaTe$_2$ at zero pressure, along with the LDOS projected onto the Fe$_{\rm I}$, Fe$_{\rm II}$, and Te atoms. The VHS1, VHS2, and VHS3 are marked in the band structure and LDOS in panel (a). The red and blue arrows represent the spin-up and spin-down LDOS, respectively. The LDOS is given in units of states/eV per f.u. (b) Corresponding FS contours in the $k_z = 0$ (left) and $k_z = \pi/c$ (right) planes.
• Figure 3: Calculated pressure-dependent LDOS for (a) Fe$_{\rm I}$, (b) Fe$_{\rm II}$, and (c) Te atoms. The arrows in panels (a) and (b) highlight the LDOS peaks near $E_F$. The maroon (cyan) arrows for the spin-up (spin-down) states in panels (a) and (b) highlight the LDOS peaks near $E_F$. In panel (c), the arrows indicate the lower ($E_{\rm min}$) and upper ($E_{\rm max}$) band edges, corresponding to the occupied and unoccupied states, respectively.
• Figure 4: Calculated pressure dependence of the spin magnetic moments of Fe$_{\rm I}$ and Fe$_{\rm II}$. The paired numbers in parentheses represent the spin-up and spin-down Fe $d$-electron counts, respectively.
• Figure 5: (a) Calculated MAE of Fe$_3$GaTe$_2$ at zero pressure, along with its angular dependence in the $xz$ and $xy$ planes as a function of the angles ${\theta}$ and $\phi$, respectively. (b) Pressure dependence of the MAE.