Tracking temperature dependent relaxation times with a wide-band quantum spectrometer

We demonstrate the tracking of the spin dynamics of ensemble and individual magnetic ferritin proteins from cryogenic up to room temperature using the nitrogen-vacancy (NV) color center in diamond as a sensor. We employ different detection protocols to probe the influence of the ferritin nanomagnets on the longitudinal and transverse relaxation of the NV-center which enables magnetic sensing over a wide frequency range. The temperature dependence can be understood by thermally induced magnetization reversals enabling the determination of the anisotropy barrier of single ferritin molecules.