Precision Multi-Mode Microwave Spectroscopy of Paramagnetic and Rare-Earth Ion Spin Defects in Single Crystal Calcium Tungstate

Elrina Hartman, Michael E Tobar, Ben T McAllister +2

We present experimental observations of dilute ion spin ensemble defects in a low-loss single crystal cylindrical sample of CaWO${}_4$ cooled to $30$ mK in temperature. Crystal field…