Ground state of bond-disordered quasi-one-dimensional spin system (CH3)2CHNH3Cu(ClxBr1-x)3 with x = 0, 0.25 and 0.3

The ground state of the quasi-one-dimensional system with bond-disorder (CH3)2CHNH3Cu(ClxBr1-x)3 with x = 0, 0.25 and 0.3 has been investigated by muSR. The Fourier spectrum of electron spin fluctuation in x =0.25 and 0.3 obtained by LF-muSR technique shows that there exists a soft-mode toward a possible phase transition to an exotic phase such as Bose-glass. In gapped system with x = 0, the Fourier spectrum is totally different from the other two, indicating the existence of the quantum critical point at a finite x between 0 and 0.25.