Clock Transition and ESEEM in the Cr₇Mn Nanomagnet

Cr₇Mn is among a family of heterometallic rings that have demonstrated remarkable chemical flexibility. The Cr₇Mn molecular nanomagnet is a spin-1 system and its two lowest spin states exhibit an avoided level crossing at zero field. At this avoided crossing, known as a clock transition, the level energies are insensitive to field fluctuations, resulting in an enhanced coherence time T₂ [1]. To further improve T₂, we employ dynamical decoupling techniques such as the CPMG pulse sequence. Cr₇Mn also exhibits a significant Electron Spin Echo Envelope Modulation (ESEEM) signal. The signal magnitude suggests that there might be alternative mechanisms for maintaining coherence, aside from clock transition, which involves coupling to nuclear spins. By using the CPMG sequence, we measured the corresponding T₂ at different fields and found it comparable to that at the clock transition. We are employing numerical calculations to identify the major decoherence channel within the system.

[1] C. A. Collett et al., Magnetochemistry 5, 4 (2019).