Electron Spin Resonance of VO$_{2}$ thin films

The metal-insulator transition present in chromium doped VO$_{2}$ nanoscale film has been observed by electron spin resonance (ESR) spectroscopy. VO$_{2}$ is a highly correlated electron system with numerous practical applications pertaining to this transition, including ultra-fast optical switching and smart windows. We use Cr$^{3+}$ transition metal ions with concentration of order one percent as a probe in a 140 nm film to detect this transition. The film exhibited a four-fold decrease in chromium intensity as temperature increased through the transition temperature ($\sim $67$^{\circ}$ C). ESR signal intensities were also used to characterize the hysteretic behavior of this particular transition; these results are in agreement with hysteresis observed through optical means. A discussion of how changes in ESR relaxation times affect signal intensities, as monitored through the transition, will be presented.