Neutron diffraction in a random two-component magnetic system: CsMn0.96Co0.04Cl3.2D2O

Neutron diffraction expriment has been performed on the quasi-one-dimensional antiferromagnet, CsMn_0.96Co_0.04Cl₃.2D₂O, in which two different magnetic ions with competing spin anistropies are randomly distributed. Magnetic scattering data show that the easy spin axis tilts substantially (～ 40° from the easy axis of Mn salt to that of Co salt at 3.8 K) even for such a dilute mixture. The magnetic ordering temperature T_N can be definitely determined owing to the absence of the diffuse Bragg intensity at T_N, to be 4.80 ± 0.02 K. The obtained value of the critical index, β = 0.23 ± 0.02 is found to be considerably smaller in magnitude than both of those found in the Mn and Co salts. Some possible origins for the small β are discussed. The concentration dependence of T_N IS analyzed in terms of the impurity-linked chain model with $\text{|J}{}_{\mathrm{<mtext>MnCo</mtext>}}\text{|}\text{k}\text{= 14.7}\text{K}$.