Hydrogen Treatment for Superparamagnetic VO2 Nanowires with Large Room-Temperature Magnetoresistance

One-dimensional (1D) transition metal oxide (TMO) nanostructures are actively pursued in spintronic devices owing to their nontrivial d electron magnetism and confined electron transport pathways. However, for TMOs, the realization of 1D structures with long-range magnetic order to achieve a sensitive magnetoelectric response near room temperature has been a longstanding challenge. Herein, we exploit a chemical hydric effect to regulate the spin structure of 1D V-V atomic chains in monoclinic VO2 nanowires. Hydrogen treatment introduced V3+ (3d(2)) ions into the 1D zigzag V-V chains, triggering the formation of ferromagnetically coupled V3+-V4+ dimers to produce 1D superparamagnetic chains and achieve large room-temperature negative magnetoresistance (-23.9%, 300 K, 0.5 T). This approach offers new opportunities to regulate the spin structure of 1D nanostructures to control the intrinsic magnetoelectric properties of spintronic materials.