Local magnetic susceptibility of the positive muon in the quasi-1D S ¼ 1=2 antiferromagnet KCuF3

We report muon spin rotation measurements of the local magnetic susceptibility around a positive muon in the paramagnetic state of the quasi-one-dimensional spin 1/2 antiferromagnet KCuF3: Signals from two distinct sites are resolved which have a temperature-dependent frequency shift which is different than the magnetic susceptibility. This difference is attributed to a muon-induced perturbation of the spin 1/2 chain. r 2002 Elsevier Science B.V. All rights reserved.