Pulsed Electrically Detected Magnetic Resonance (pEDMR) at Low Magnetic Fields using an Arbitrary Wave Form Generator (AWG)

We use pulsed electrically detected magnetic resonance (pEDMR) in order to observe the coherent propagation of electron spins under strong drive magnetic resonance conditions in organic materials, where excitation frequencies (~100 MHz) and Zeeman fields (~3 mT) are low. In these materials, transverse relaxation times of electron spins are known to be in the on the order to 1µs [1], requiring the bandwidths of the pulse experiments to be in the 10-100 MHz range in order to accommodate effective pulse sequences. Thus, at low excitation frequencies [2,3], the duration of spin manipulation pulsed becomes comparable to the carrier-wave frequency, and conventional methods for generating RF pulses become impossible. We therefore utilize an arbitrary waveform generator (AWG) to directly synthesize RF pulses with a shape derived directly from the desired excitation spectrum. We evaluate the fidelity of such pulsed low-frequency excitation and conduct experiments that demonstrate electrically detected coherent spin motion under the given low-field conditions.[1] R. Miller, et al.,Phys. Rev. B, 94, 214202 (2016); [2] S. Jamali et al., Nano Lett. 4648 (2017); [3] D. P. Waters et al., Nature Physics 11, 910 (2015).