Ordering in weakly coupled random singlet spin chains

Abstract

The influence of bond randomness on long range magnetic ordering in the\nweakly coupled S = 1/2 antiferromagnetic spin chain materials\nCu(py)2(Cl1-xBrx)2 is studied by muon spin rotation and bulk measurements.\nDisorder is found to have a strong effect on the ordering temperature TN, and\nan even stronger one on the saturation magnetization m0, but considerably more\nso in the effectively lower-dimensional Br-rich materials. The observed\nbehavior is attributed to Random Singlet ground states of individual spin\nchains, but remains in contradiction with chain mean field theory predictions.\nIn this context, we discuss the possibility of a universal distribution of\nordered moments in the weakly coupled Random Singlet chains model.\n