Magnetic sensing with silicon vacancies in isotopically purified 4H-SiC

The silicon vacancy center in 4H-SiC is an optically active defect with spin transitions that can be initialized and read out at room temperature. The sensitivities of room temperature magnetometers using these defects have been limited by decoherence due to a magnetically noisy host crystal. In this work we demonstrate coherence time improvements of silicon vacancy ensembles via isotopic purification of SiC and through a novel choice of basis in the S=3/2 ground state of the defect. Using this, we realize a broadband room temperature magnetometer with a 4nT/rt(hz) sensitivity and a 200pT/rt(Hz) shot noise limited sensitivity.