Novel bipolar magnetic semiconductor materials formed by adsorption of methyl or halomethyles on the graphene: A spin-polarized density functional theory study

Abstract

Exploring magnetic materials with electrically controlled spin polarization and room temperature magnetic ordering is of particular importance for applications in spintronic devices. In this study, we present a detailed theoretical study on the structural, electronic, and magnetic features of pristine graphene on which methyl(CH3) or a halomethyl (CH2F, CH2Cl, CH2Br, or CH2I) radical has been adsorbed. The framework of our calculations is dispersion-corrected density functional theory with due account of the spin degree of freedom within the Quantum-ESPRESSO package. The investigation starts with a complete discussion of the geometrical characteristics, followed by a thorough study of the manner of charge transfer and redistribution, electronic band structures, and density of states. The calculated adsorption energies and distances demonstrate the adsorption process to be of the chemisorption type. The adsorption of each radical on graphene is accompanied by a net charge transfer, changing the work function of the resulting compounds and modulating the electronic and magnetization characteristics of pristine graphene. Considerations of the calculated spin-distinct electronic band structure and density of states support the latter conclusion. The presence of unequal band gaps in the up and down spin channels also corroborates the aforementioned compounds' bipolar magnetic semiconductor nature.