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 MoB _4 and MoB _6 , are such candidates with high thermal and dynamical stabilities. MoB _4 and MoB _6 are characterized as either ferromagnetic or antiferromagnetic metals. Notably, both MoB _4 and MoB _6 display sizable magnetic anisotropy energy—924 and 932 μ eV per Mo atom, respectively—surpassing that of the widely studied CrI _3 monolayer, which measures 685 μ eV per Cr atom. Monte Carlo simulation suggests the Curie temperature of MoB _4 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 MoB _4 and AC-stacked MoB _6 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.

Keywords

• first-principles calculation
• 2D materials
• ferromagnetism
• Curie temperature