Pr. Hammar et Dh. Reich, CU-2(1,4-DIAZACYCLOHEPTANE)(2)CL-4 - A QUASI-ONE-DIMENSIONAL S=1 2 SPIN LIQUID-SYSTEM/, Journal of applied physics, 79(8), 1996, pp. 5392-5394
The structure of Cu-2(1,4-diazacycloheptane)(2)Cl-4 consists of well-s
eparated zig-zag chains of Cu atoms, suggesting the possibility of sig
nificant antiferromagnetic near-neighbor and next-nearest-neighbor int
eractions. We report on measurements of magnetic susceptibility (chi)(
H,T) and heat capacity C-p(T) that show that this material does not be
have as a simple linear antiferromagnetic chain with spin S=1/2. (chi)
(H=0,T) shows a broad peak at 8 K indicative of one-dimensional antife
rromagnetic correlations, but below the peak, chi drops dramatically t
oward zero instead of remaining finite as T-->0. For T much less than
T (peak), (chi)(H) is independent of field below a critical field H-c
approximate to 6.6 T, and rises sharply above H-c to a plateau at 8 T.
Below T-peak, C-p(T)proportional to exp(-Delta/T) with an activation
energy Delta=6.8 K. These data indicate the presence of a gap between
the ground state and the lowest-lying excited states. This material is
thus a candidate for a model quasi-one-dimensional S=1/2 system with
a disordered ground state that is significantly affected by competing
interactions. (C) 1996 American Institute of Physics.