A Clock Transition in the Cr${}_7$Mn Molecular Nanomagnet

Abstract

A viable qubit must have a long coherence time $T_2$. In molecular nanomagnets $T_2$ is often limited at low temperatures by the presence of dipole and hyperfine interactions, which are often mitigated through sample dilution, chemical engineering and isotope substitution in synthesis. Atomic-clock transitions offer another route to reducing decoherence from environmental fields by reducing the effective susceptibility of the working transition to field fluctuations. The Cr${}_7$Mn molecular nanomagnet, a heterometallic ring, features a clock transition at zero field. Both continuous-wave and spin-echo electron-spin resonance experiments on Cr${}_7$Mn samples diluted via co-crystallization, show evidence of the effects of the clock transition with a maximum $T_2\sim 350$ ns at 1.8 K. We discuss improvements to the experiment that may increase $T_2$ further.

4 pages, 4 figures, submitted to Magnetochemistry