THEORETICAL-STUDY ON ORGANIC ONE-DIMENSIONAL FERRIMAGNETS

The magnetic susceptibility chi(T) of one-dimensional ferrimagnets con sisting of two kinds of quantum spins S-1 and S-2 are calculated by th e dynamical correlated-effective-field approximation (DCEFA). At high temperatures chi(T) obeys the Curie-Weiss law with a negative Weiss te mperature. As the temperature is decreased, chi(T) diverges towards T = 0K according to chi(T) congruent to 4(g mu B)(2)/9\J\ root X1X2(root X-1 - root X-2)(2)(\J\/k(B)T)(2) with X-1 = S-1(S-1 + 1) and X-2 = S- 2(S-2 + 1). chi(T) has been calculated also by the exact diagonalizati on method (EDM) for the case of S-1 = 1 and S-2 = 1/2. It is found tha t chi(T) obtained by the DCEFA agrees well with that obtained by the E DM in the whole temperature range. The observed susceptibility of an o rganic one-dimensional ferrimagnet Mn(II)(hfac)(2)(dipycarbene) (S-1 = 5/2 and S-2 = 1 system) has been analysed by DCEFA and the exchange c oupling is estimated to be -15 K.