Hybrid Electron Spin Resonance and Whispering Gallery Mode Resonance Spectroscopy of Fe3+ in Sapphire

Abstract

The development of a new era of quantum devices requires an understanding of how paramagnetic dopants or impurity spins behave in crystal hosts. Here, we describe a new spectroscopic technique which uses traditional Electron Spin Resonance (ESR) combined with the measurement of a large population of electromagnetic Whispering Gallery (WG) modes. This allows the characterization of the physical parameters of paramagnetic impurity ions in the crystal at low temperatures. We present measurements of two ultra-high purity sapphires cooled to 20 mK in temperature, and determine the concentration of Fe3+ ions and their frequency sensitivity to a DC magnetic field. Our method is different to ESR in that it is possible to track the resonant frequency of the ion from zero applied magnetic field to any arbitrary value, allowing excellent measurement precision. This high precision reveals anisotropic behaviour of the Zeeman splitting, which has not been previously reported. In both crystals, each Zeeman component demonstrates a different g-factor.

10 pages, 11 figures

References in corpus (3)

• Revised value of the eighth-order QED contribution to the anomalous magnetic moment of the electron
• Measurement of fundamental thermal noise limit in a cryogenic sapphire frequency standard using bimodal maser oscillations
• Low-loss Materials for high Q-factor Bragg Reflector Resonators

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• Aggregate Frequency Width, Nuclear Hyperfine Coupling and Jahn-Teller Effect of $C{u}^{2+}$ Impurity Ion ESR in $SrLaAl{O}_4$ Dielectric Resonator at $20$ Millikelvin
• Rigorous ESR spectroscopy of $F{e}^{3+}$ impurity ion with oxygen vacancy in ferroelectric $SrTi{O}_3$ crystal at 20 mK