Spectroscopic Observation of Electric Field Effects in the [VO(TPP)] Nanomagnet

Vanadyl oxide tetraphenylporphyrin, or [VO(TPP)], is a molecular nanomagnet that exhibits long coherence times and strong hyperfine coupling between the molecule’s S = 1/2 electronic spin and the vanadyl I = 7/2 nuclear spin. Using electron-spin resonance (ESR) spectroscopy in S-band, we can sweep a varying external magnetic field while applying continuous wave radiation to induce transitions between spin states in a crystal of [VO(TPP)]. Capacitor plates placed in the loop-gap resonator allow us to apply a static electric field of controlled strength directly to our sample while measuring the ESR spectrum. At low applied electric fields, we observe eight spin-state transitions consistent with the established hyperfine coupling for this molecule. However, there exists a critical field strength of ?3x10^5 V/m, above which the eight transitions nearly disappear and are replaced by a single strong ESR line. We present the experimental apparatus utilized to characterize this behavior and our planned next steps.