Experimental Estimates of Dephasing Time in Molecular Magnets

Muon spin relaxation measurements in isotropic molecular magnets (MM) with a spin value S ranging from 7/2 to 27/2 are used to determine the magnitude and origin of dephasing time τ_ϕ of molecular magnets. It is found that τ_ϕ∼10  nsec with no S or ligand dependence. This indicates a nuclear origin for the stochastic field. Since τ_ϕ is a property of the environment, we argue that it is a number common to similar types of MM. Therefore, τ_ϕ is shorter than the Zener and tunneling times of anisotropic MM such as Fe₈ or Mn₄ for standard laboratory sweep rates. Our findings call for a stochastic Landau-Zener theory in this particular case.