Induction of stable, room-temperature ferromagnetism in WO3 by doping with K, Li, and Na: Theoretical investigations

Abstract

Inducing ferromagnetism in non-magnetic materials via doping with non-transition metals can provide persistent and stable magnetism toward spintronics application. Using density functional theory, we predict induced ferromagnetism (5 µB) in 3.13 at.% Li-, Na-, and K-doped monoclinic WO3. The strength of induced magnetism is influenced by the concentration of dopants. The induced magnetism is primarily contributed by the 2p orbital of O atom in doped-WO3, substantiated by spin-density analysis and Bader charge portioning. Cation substitutional doping, i.e., replacing a W+6 with monovalent alkaline metals like Li+, Na+, or K+, tends to inject five holes in the resultant system. The Curie temperatures computed using the mean field approximation exceeds room temperature for all the three systems, indicating persistent magnetism at room temperature. The stability of the magnetism at room temperature was confirmed via ab initio molecular dynamics simulations. The probable mechanism of magnetism and aspects related to the experimental feasibility of these systems have been studied. This work presents another avenue for exploration for the preparation of dilute magnetic semiconductors toward spintronics applications.