Thickness-dependent magnetic anisotropy in two-dimensional layered rare-earth electride Gd2C

The recently synthesized layered electride Gd2C exhibits an in-plane easy magnetization axis (EMA) in samples exfoliated from the bulk. However, a detailed understanding of the underlying mechanisms of this magnetic anisotropy has been lacking. Our first-principles DFT + U calculations reveal that the EMA is determined by the interplay of magnetocrystalline anisotropy, driven by spin-orbit coupling, and shape anisotropy, stemming from dipole-dipole interactions, with their relative contributions varying as a function of film thickness. The magnetocrystalline anisotropy energy, which favors the out-of-plane direction, decreases sharply with increasing thickness, while the shape anisotropy energy, favoring the in-plane direction, declines more gradually due to its long-range nature. Consequently, the monolayer displays an out-of-plane EMA, while thicker films exhibit an in-plane EMA, consistent with experimental observations, and the EMA reverts to the out-of-plane direction in the bulk. Our analysis indicates that interorbital couplings in the Gd 4f orbitals contribute significantly to the magnetocrystalline anisotropy energies, with both positive and negative components that largely cancel each other out, highlighting the Gd 5p orbitals as the dominant factor. The magnetocrystalline anisotropy from the Gd 5p orbitals is markedly enhanced in the monolayer compared to the bulk, primarily due to band shifts caused by charge redistribution at the monolayer surface. These findings offer a comprehensive understanding of the thickness-dependent magnetic anisotropy in Gd2C and underscore its potential in nanoscale magnetic devices, where shape anisotropy and surface effects play a crucial role. locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon locked icon Physics Subject Headings (PhySH)First-principles calculationsMagnetic anisotropySpin-orbit couplingFerromagnetsTwo-dimensional electron systemDensity functional theory