EPR OF SOME VERDAZYL FREE RADICALS LOW DIMENSIONAL BEHAVIOR

Verdazyl自由基是一类具有吸引力的化合物

Verdazyl free radicals are a family of compounds with attractive organic/molecular ferromagnetic properties. Previous studies have shown that the linewidth of a single line EPR spectrum from polycrystalline verdazyl samples varies with themolecular structure. EPR linewidth data at various temperatures correlate with magnetic susceptibility revealing a ferromagnetic phase transition at low temperatures. In the present work we examine angular variation of EPR linewidth of some novel types of verdazyl radicals available in a crystal form. Observed linewidths have a "W-shape" angular dependence that is characteristic for low-dimensional (1- or 2-D) spin systems. Linewidth angular dependence was used to separate secular and nonsecular contributions to the EPR lineshape. EPR can reveal the low-dimensionality of the spin system even at room temperature, while magnetic susceptibility data in a wide temperature range are required to provide a basis for assigning a certain model for the spin-sp in interactions in the system.