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In a longitudinalμ+SR experiment on a high-purityα-Fe single crystal sphere magnetically saturated in a 〈 111 〉 direction damped oscillations (wiggles) were observed in a temperature range 30 mK to 600 mK and in a certain regime of applied magnetic fieldsBappl. Meassurements of the wiggle frequency as a function ofBappl give us directly the Fermi fieldBFermi=(−1.13±0.02)T and the dipolar magnetic field ¦Bdip∥¦=(0.66±0.03)T.Bdip∥ was used to determine the prefactor in the Arrhenius law obeyed by theμ+ hopping rate between 100 K and 1000 K. A comparision with the corresponding values for protons and deuterons suggests diffusion via the adiabatic mechanism.

Abstract: The spin-precession frequencies and the transverse spin relaxation rates of positive mouns (μ +) have been measured on two elastically strained α-Fe single crystal platelets as well as on an unstrained reference α-Fe crystal at temperatures down to 2.7 K in applied magnetic field 0≤B appl≤3 T. The drastic effects of the strains may be qualitatively understood in terms of their influence on both the magnetic domain structure and theμ + energies at the various interstitial sites. This leads to the conclusion that at low temperaturesμ + in α-Fe occupy configurations related to octahedral interstitials with dipolar fieldB dip=0.70 T.

Abstract: μ + SR measurements have been performed on Cr single crystals at temperatures 60 mK≤T≤295 K in applied magnetic fields 0≤B appl≤1.5 T. The temperature dependence of the observed precession frequencies and transverse relaxation rates can be explained by the assumption that theμ + are hopping between adjacent tetrahedral interstices. At temperaturesT≤11 K evidence for an interaction between theμ + and the spin-density waves in Cr has been found. The directions and magnitudes of the lattice magnetic moments are unaffected by the applied magnetic fields.

Abstract: The longitudinalμ +-spin relaxation rate has been measured on a high-purity spherical α-iron single crystal at temperaturesT down to 20 mK and in applied magnetic fieldsB appl parallel to 〈111〉 up to 3 T. Only above 1 K can the data be satisfactorily described by one rate constantГ. At 1 T≤B appl≤2 T and 50 mK≤T≤300 mK, oscillations (“wiggles”) were in addition superimposed on the longitudinal relaxation. A qualitative understanding of the measurements may be achieved in terms of the increasing influence of internal stresses onμ + diffusion as the temperature is lowered.

Abstract: μ− SR experiments have been performed on Si between room temperature and 6 K. The amplitude of the muon spin precession signal in an applied magnetic field of 0.04 T decreased below 30 K. A zero-field measurement at 6 K revealed a μ− spin precession frequency of 650 MHz. The muonic atom represents an aluminium acceptor in the silicon matrix, its electronic state is responsible for the μSR signal. A possible influence of the γ recoil produced by the X-ray cascade is discussed.