Longitudinal spin-relaxation in nitrogen-vacancy centers in electron irradiated diamond

We present systematic measurements of longitudinal relaxation rates ( 1/T1) of spin polarization in the ground state of the nitrogen-vacancy (NV–) color center in synthetic diamond as a function of NV– concentration and magnetic field B. NV– centers were created by irradiating a Type 1b single-crystal diamond along the [100] axis with 200 keV electrons from a transmission electron microscope with varying doses to achieve spots of different NV– center concentrations. Values of ( 1/T1) were measured for each spot as a function of B.