Electron-spin diffusion in proton-irradiation microstructured (fluoranthene)2PF6

Abstract

The properties of the quasi-one-dimensional organic conductor (fluoranthene)${}_{2}{\mathrm{PF}}_{6}$ are modified by proton irradiation ${(E}_{p}=25\mathrm{MeV},$ ${n}_{p}=5.4\ifmmode\times\else\texttimes\fi{}{10}^{16}{\mathrm{cm}}^{\ensuremath{-}2}).$ The crystals are characterized by measurement of static magnetic susceptibility, cw--electron spin resonance, static magnetic-field gradient pulsed electron spin resonance and especially by one- and two-dimensional electron-spin-resonance imaging. Electron-spin diffusion constant parallel to the stacking direction is reduced by one order of magnitude, whereas the perpendicular direction remains essentially unchanged, for homogeneous proton irradiation. A well-defined periodic $100\ensuremath{-}\ensuremath{\mu}\mathrm{m}$ structure is impressed using appropriate metal grids in the proton beam. Thus the diffusion constant, as well as the concentration of localized defects, is spatially modulated. Experimental evidence of the coherence phenomena of the diffusing electron spins moving between the artificially created reflecting walls is presented.