μ+SR Spectroscopy: The Positive Muon as a Magnetic Probe in Solids

Abstract
Through its asymmetric decay, the positive muon acts as a sensitive detector of the interactions of its spin with the medium in which it comes to rest. Development of the μ+SR spectroscopy technique is described, and recent applications of the μ+ as a probe are discussed. Results for hyperfine fields in ferromagnets and impurity states in nonmetals are presented with suggestions for future studies.