ANOMALOUS ZERO-FIELD MUON SPIN RELAXATION IN HIGHLY DISORDERED MAGNETS

Low-temperature zero-field muon spin relaxation spectra from several d isordered magnetic materials show static-field relaxation behavior tha t cannot be properly represented by the Gaussian or Lorentzian distrib utions commonly used in the analysis of such data (Kubo-Toyabe relaxat ion). In the case oi CeCu0 2Ni0.8Sn, a Gaussian distribution of second moments, convoluted with a Gaussian form of field distribution, produ ces a closed-form modified Kubo-Toyabe relaxation function that fits t he data well. Its characteristic feature is a shallow polarization min imum before recovery to the 1/3 asymptote. Any microscopic model that reproduces such shallow static Kubo-Toyabe relaxation must do so by ge nerating an excess of low-field sites.