MAGNETIC EXCITATION SPECTRUM IN LARGE-D CHAIN NENC

EPR studies of the single crystals of NENC (Ni(C2H8N2)(2)Ni(CN)(4)) wh ich can be regarded as a large-D Heisenberg spin chain system have bee n performed for different orientations of external magnetic field. Var ious magnetic field dependent resonances were observed. The magnetic e xcitation spectrum is discussed within the framework of the single-ion model. Several excitation branches can be interpreted quantitatively. Peculiarities of the transition in the magnetic phase in applied magn etic field at B-cr = 4.4 T (B parallel to z) are discussed. The value of the observed gap in the excitation spectrum is in good agreement wi th the results of a strong-coupling theory of (anti)excitons.