Noise spectrum modeling for the Cr₇Mn molecular magnet probed using dynamical decoupling

Cr₇Mn is a spin-1 molecular nanomagnet (MNM) with an avoided level crossing at zero field, known as a clock transition (CT). In this system, we observe an enhancement in coherence time at the CT as well as at higher fields where Electron Spin Echo Envelope Modulation (ESEEM) occurs. We employed the CPMG pulse sequence to characterize Cr₇Mn's decoherence behavior and performed simulations to extract the noise spectrum seen by the spin. The model provides insights into the primary mechanisms of decoherence in the system. Fitting our data, we find that the system's noise spectrum consists primarily of two distinct sources: 1) magnetic fluctuations near the proton Larmor frequency, and 2) fluctuations in the molecule's anisotropy, which modulates the clock transition frequency itself, possibly arising from spin-vibrational coupling. The model may be applied to a broader family of spin systems (e.g., other MNMs).