Determination of very slow. mu. /sup +/ hop rates in Cu by LLF-. mu. SR Page: 2 of 8
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DETERMINATION OF VERY SLOW u* BOP RATES IN Cu BY LLF-jxSR
J.H. Brewer, M. Celio, D.R. Harshman, R. Keitel, S.R. Kretlzman,
C.M. Luke, D.R. Noakes and R.E. Turner, TRIUMF, 4004 Wesbrook
Mall, Vancouver, B.C., Canada V6T 2A3
E.J. Ansaldo, Dept, of Physics, University of Saskatchewan,
Saskatoon, Saskatchewan, Canada S7N 0W0
C. W'. Clawson* and K.M. Crowe, Lawrence Berkeley Laboratory,
University of California, Berkeley, California, USA 94720
C.Y. Huang, Los Alamos National Laboratory, Los Alamos, NM, USA
Muon spin relaxation in low (weak) longitudinal magnetic
field (LLF-aSR) provides a means of independently
determining the static dipolar width A characterizing
the a* lattice site and the correlation time rc| for it£
hopping, in a manner that is nearly model-independent
for rc and especially accurate in the near-static limit
<r > r^). The advantages of this method are
illustrated by its application to muon hopping in Cu
near the t„ maximum around 5(f R.
Positive muon spin relaxation (*<*SR) has found one of its
main applications in the investigation of u* diffusion (analogous
to hydroyen diffusion) in metals, by virtue of the "motional
narrowing" effect of muon "hopping" on the relaxation rate./l/
The classic example of this application is it* diffusion in copper,
where the temperature dependence of the it* motion above 80 K is
well understood in terms of thermally activated muon tunneling
between octahedrally coordinated interstitial sites (o-sites)
where the muon is localized by self-trapping [see summary of
various authors' work in Ref. 1]. In 1979, transverse-field
(TF)-jiSR experiments at CERN/2/ indicated that the correlation
time r. for a* hopping in Cu decreases with decreasing T below
about 50 K, levelling off below about 0.3 R to a value
approximately equal to that at 130 R. This surprising result
stimulated considerable theoretical speculation about the
Although the field-dependence of the effective relaxation
rate was consistent with it* hopping between o-sites,/2/ the TF-aSR
time spectra themselves did not offer much model-specific
information. Zero-field (ZF)-aSR experiments were therefore
performed at TR2UMF/5/ and BOOM/6/ to take advantage of the
superior sensitivity of ZF-«tSR time spectra to the details of the
relaxation mechanism — particularly to the decay of the tail"
of the Rubo-Toyabe (RT) relaxation function/7/ due to slow hopping
of the a* between o-sites. The results were entirely consistent
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Brewer, J.H.; Celio, M.; Harshman, D.R.; Keitel, R.; Kreitzman, S.R.; Luke, G.M. et al. Determination of very slow. mu. /sup +/ hop rates in Cu by LLF-. mu. SR, article, January 1, 1986; United States. (digital.library.unt.edu/ark:/67531/metadc1063684/m1/2/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.