Magnetic Regulation in Negatively Charged Hydrogen Vacancy Defect Nanodiamond Driven by Intrinsic H-Mobility and External Electric Field

Abstract

The development of open-shell diamond-like magnetic materials shows promise due to their unique stability in comparison to reactive sp2 carbon-based magnets. The negatively charged hydrogen-vacancy (VH^–) center is a common point defect in diamond, yet the magnetic spin coupling between carbon radicals in VH^– centers is not well understood. This study, using spin-polarized density functional theory (DFT) calculations, explores dynamic magnetic coupling among carbon radicals, driven by intrinsic hydrogen migration and external electric fields. Internal hydrogen migration induces magnetic switching between ferromagnetic (FM, J = 1599.58 cm^–1) and antiferromagnetic (AFM, J = −221.85 cm^–1) states via electron-coupled proton transfer, which redistributes excess electron density. Additionally, the FM strength exhibits a pronounced directional dependence in response to the applied electric field. Along the y-axis, the field disrupts the symmetric electron distribution among the three-center carbon radicals, effectively modulating the FM coupling with a strength variation ΔJ_y = 2170.80 cm^–1, while along the z-axis (perpendicular to the radicals’ plane), the FM coupling strength shows minimal perturbation. These findings suggest VH^– centers hold great potential for spintronic applications, particularly in extreme environments (temperature and E-field), where tunable properties can aid novel device development.