We have observed strong muon-spin relaxation (CBR) in the spin-Peierls comp
ound MEM(TCNQ)(2) at temperatures down to 39 mK. We attribute this relaxati
on to the creation of defect spins by the muon. Furthermore, we observe a s
lowing down of spin fluctuations as the spin-Peierls energy gap opens, and
we relate this effect to the size of the energy gap. (C) 2000 Elsevier Scie
nce B.V. All rights reserved.