What can muons tell us about condensed matter ? – Niels Bohr Institute - University of Copenhagen

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What can muons tell us about condensed matter ?

To a particle physicist a muon is a member of the lepton family, a heavy electron with 1/9 the mass of a proton and a spin of 1/2. Since its discovery in 1937, the muon has played a prominent role for tests of special relativity, weak interactions and quantum electrodynamics. In 1957 Richard Garwin and collaborators discovered that spin-polarized muons injected into materials might be useful to probe internal magnetic fields. This gave birth to the field of μSR, which stands for muon spin rotation, relaxation or resonance. Today, the SR technique is a powerful tool for studying the spatial distribution and temporal fluctuations of internal magnetic fields within solids. µSR gives information that is complementary to that provided by scattering techniques. The extreme sensitivity for the detection of local magnetic fields makes it an invaluable tool for the study of systems with very small, dilute or random ordered moments. Its unique time window for studies of dynamical processes bridges the gap between fluctuation rates probed by NMR and neutron scattering. After an introduction to the technique, some examples of muon spin rotation studies in solid state physics will be presented.

Talk by Christof Niedermayer