Vanadium dioxide (VO2) has long held promise as a functional material due to its unique phase transition near room temperature where it switches from one insulating crystal structure to a different metallic crystal structure. Hybrid structures where a magnetic thin film is deposited onto the VO2 can allow for novel functionality due to coupling between the two materials. In this work, we studied the magnetic properties of Nickel films deposited onto both phases of VO2. Both types of bilayers show strong enhancement of the magnetic coercivity (the resistance to change in the orientation of the magnetic domain structure) near the VO2 phase transition. While some samples show complete reversibility under thermal cycling, other samples show an irreversibility after the first cycle. This irreversibility may be associated with cracking in the VO2 as it strains itself through the phase transition. Cracking also has implications for the conductive properties of the VO2. Modeling that includes cracking reproduces the changes in the film’s conductance. These results show that initial growth conditions for the bilayers can be critical to tune properties of the bilayer close to room temperature, making it attractive for technological applications.
J. Lauzier, L/. Sutton and J. de la Venta, Journal of Physics: Condensed Matter 30, 374004 (2018) (https://doi.org/10.1088/1361-648X/aad5af)