  The antiferromagnetic ordering in the solid-solution of the two spin-gap
systems (CH3)2CHNH3CuCl3 and (CH3)2CHNH3CuBr3 has been investigated by 1H-NMR.
The sample with the Cl-content ratio x=0.85 showed a clear splitting in spectra
below TN=13.5 K, where the spin-lattice relaxation rate T1-1 showed a diverging
behavior. The critical exponent of the temperature dependence of the hyperfine
field is found to be 0.33.
