Magnetic interaction and spin diffusion in solvent-free DPPH

Susceptibility and ESR measurements are performed on single crystals of solvent-free 2,2-diphenyl-1-picrylhydrazyl (DPPH) in a temperature range of 1.5–300 K. The susceptibility measurements are explained by pair model (2Jk = -17.6 K) but in contrast to previous powder data about 4% non-pairing paramagnetic centres are observed at low temperatures. As these centres probe the dynamics of the spin system the line width data may be explained by a low-dimensional diffusion model.