Neutron Diffraction Study in One-Dimensional Antiferromagnet KCuF3

In order to examine the universal nature in quasi-one-dimensional magnetic system, a detailed neutron-diffraction investigation of the magnetic properties of antiferromagnet KCuF 3 has been carried out. A qualitative analysis of the wave-vector-dependent susceptibility above the Néel temperature has been performed near the (001) position in reciprocal space. The topological features of the (001) diffuse peak were utilized to ascertain the one-dimensional nature and the relative values of J c and J a , intra- and interchain exchange interaction, respectively. On applying a resolution-correction procedure we obtain J a / J c =0.027±0.005 at 39.800 K. On the other hand, below T N the sublattice magnetization is found to follow the power law M T / M 0 = D (1- T / T N ) β , with D =1.53±0.05, T N =39.51±0.02 K and β=0.355±0.010, for the temperature interval 0.001< T N - T / T N <0.1. The exponent β is in excellent agreement with the three-dimensional spin-half isotropic Heisenberg value 0.354. And for T / T N <0.65 the temperature variation of sublattice magnetization is found to follow the T 2 -law.