Mapping the dynamic properties of electron spins in the organic conductor (FA)2PF6

Pulsed ESR is used for microscopic three-dimensional imaging of the conduction electron spin properties in the organic crystal (FA)2PF6 (FA: fluoranthene). The measurements enable a study of the local properties of the electron spins on the scale of ∼30μm. The ‘local’ aspect of the information gained is found to be important, as the images generally exhibit pronounced inhomogeneity. The properties investigated so far are spin relaxation times and mobility. The relaxation times, T1 and T2, were found each to vary by a factor of ∼2 within the samples, and their variations are highly correlated with one another. The spin diffusion might be varying too, in negative correlation with the relaxation times. Viewing the relaxation maps, surface effects are also discernible in some of the samples.