Magnetic characterization of one-dimensional systems composed of nitronylnitroxide radicals as studied by ESR and susceptibility measurements

We synthesized a novel organic radical, 3,4-dichlorophenyl nitronyl nitroxide and characterized magnetic properties in the solid state. An X-ray crystal structure analysis revealed that this molecule formed one-dimensional regular chains in the crystal. Temperature dependence of magnetic susceptibility was reproduced by the antiferromagnetic regular chain model with an exchange interaction J/k_B = -8.0 K, which is consistent with the crystal structure. The radical crystal is an example of the regular spin chain in the organic systems that exhibits the largest exchange interaction. Single-crystal cw-ESR exhibited a temperature-dependent shift of g-value. The physical origin of the g-shift is discussed by comparing the observed data with theories describing the short range order effect in antiferromagnetic spin chains. The possibility of demagnetizing field effect on the g-shift in the paramagnetic crystal is also referred.