  The physics of the metal-insulator transition (MIT) in vanadium dioxide
remains a subject of intense interest. Because of the complicating effects of
elastic strain on the phase transition, there is interest in comparatively
strain-free means of examining VO2 material properties. We report contact-free,
low-strain studies of the MIT through an inductive bridge approach sensitive to
the magnetic response of VO2 powder. Rather than observing the expected
step-like change in susceptibility at the transition, we argue that the
measured response is dominated by an analog of the Barkhausen effect, due to
the extremely sharp jump in the magnetic response of each grain as a function
of time as the material is cycled across the phase boundary. This effect
suggests that future measurements could access the dynamics of this and similar
phase transitions.
