Coherence times and Rabi oscillations in CaWO4:Cr5+ crystal

► Coherence times of Cr5+ ions in CaWO4 are investigated. ► Phase relaxation is due to magnetic dipole interactions. ► Anomalously fast damping of Rabi oscillations is detected. ► The decay of Rabi oscillations is due to inhomogeneity of microwave field. ► Lumped-element resonators are suggested to reduce decay rate of Rabi oscillations.