Two-dimensional Mo decorated borophenes: high critical temperature, large magnetic anisotropy, and stacking-dependent magnetism

Abstract

Two-dimensional magnetic materials with high critical temperature, large magnetic anisotropy energy and intrinsic magnetism hold great promise for advancements in spintronics. However, synergizing these attributes within a single material remains challenging. Through the application of swarm-intelligence-based structure searching along with first-principles calculations, we identify two Mo decorated borophene variants, denoted as MoB4 and MoB6, are such candidates with high thermal and dynamical stabilities. MoB4 and MoB6 are characterized as either ferromagnetic or antiferromagnetic metals. Notably, both MoB4 and MoB6 display sizable magnetic anisotropy energy—924 and 932 μeV per Mo atom, respectively—surpassing that of the widely studied CrI3 monolayer, which measures 685 μeV per Cr atom. Monte Carlo simulation suggests the Curie temperature of MoB4 sheet is 390 K, which is above room temperature. Our examination uncovers that bilayer Mo x B y formations exhibit layer-specific van der Waals interactions, contrasting with bilayer borophenes produced experimentally, which display robust interlayer chemical bonding. We determine that the stacking order profoundly influence both the magnetic anisotropy energy and critical temperatures of the material. Specifically, the magnetic anisotropy energy for both structures doubles in their bilayer configurations, with AB-stacked MoB4 and AC-stacked MoB6 demonstrating critical temperatures of 550 K and 320 K, respectively. The exceptional electronic and magnetic characteristics of the Mo x B y monolayers position them as favorable candidates for future spintronic devices.