Magnetism in purple bronze Li$_{0.9}$Mo$_6$O$_{17}$
  Muon spin relaxation measurements around the 25 K metal-insulator transition in Li$_{0.9}$Mo$_6$O$_{17}$ elucidate a profound role of disorder as a possible mechanism for this transition. The relaxation rate $1/T_1$ and the muon Knight shift are incompatible with the transition to a SDW state and thus exclude it. 
J. Chakhalian, Z. Salman, J. Brewer, A. Froese, J. He, D. Mandrus, R.   Jin