Hyperfine interactions and coherent spin dynamics of isotopically purified ¹⁶⁷Er³⁺ in polycrystalline Y₂O₃

Er-167(3+) doped solids are a promising platform for quantum technology due to erbium's telecom C-band optical transition and its long hyperfine coherence times. We experimentally study the spin Hamiltonian and dynamics of Er-167(3+) spins in Y2O3 using electron paramagnetic resonance (EPR) spectroscopy. The anisotropic electron Zeeman, hyperfine and nuclear quadrupole matrices are fitted using data obtained by X-band (9.5 GHz) EPR spectroscopy. We perform pulsed EPR spectroscopy to measure spin relaxation time T-1 and coherence time T-2 for the 3 principal axes of an anisotropic g tensor. Long electronic spin coherence time up to 24.4 mu s is measured for lowest g transition at 4 K, exceeding previously reported values at much lower temperatures. Measurements of decoherence mechanism indicates T-2 limited by spectral diffusion and instantaneous diffusion. Long spin coherence times, along with a strong anisotropic hyperfine interaction makes Er-167(3+):Y2O3 a rich system and an excellent candidate for spin-based quantum technologies.