Muon spin relaxation in a random ferromagnet: PdMn
Gist, Grant Alan
Dodds, Stanley A.
Master of Arts
Muon spin relaxation (ySR) experiments have been performed in transverse, longitudinal and zero applied field on the disordered ferromagnet PdMn (2.3 at.%). Muon relaxation rates in the paramagnetic phase are in good agreement with predictions of the Walstedt-Walker formula, and appear to have no contribution from muon coupling to the giant moment polarization cloud. The transverse field relaxation rate (yT) and the width of x the zero field quasistatic field distribution (a(T)) in the ferromagnetic phase are less than calculated from a uniform mean field model. This "shortfall" is found to be qualitatively consistent with the Sherrington-Kirkpatrick disordered mean field theory. Spin-lattice relaxation rates in zero applied field give clear evidence for critical slowing down of Mn spin fluctuations over a wide temperature range, and are consistent at low temperatures with a two magnon Raman scattering mechanism.