Spin dynamics in crystalline and amorphous DyAg |
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Authors: | G M Kalvius L Asch D R Noakes R Keitel J H Brewer E J Ansaldo F J Litterst B Boucher J Chappert A Yaouanc T Yamazaki K Nagamine K Nishiyama O Hartmann R Wäppling |
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Institution: | (1) Technical University, Munich, FGR;(2) TRIUMF, Vancouver, Canada;(3) University of Saskatchewan, Saskatoon, Canada;(4) CEN Saclay, Fance;(5) CEN Grenoble, France;(6) University of Tokyo, Japan;(7) University of Uppsala, Sweden |
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Abstract: | Crystalline (cr-) Dyag CsC] structure] orders antiferro-magnetically with TN≅60K; amorphous (am-) DyAg ferro-magnetically with TC≈-18K. We measured the longitudinal field (LF) μ+SR relaxation functions GZZ(t) for 5K<T<300K using surface muons. In the paramagnetic state. cr-DyAg gives an exponential GZZ (t) in the relaxation rate rising first slowly then more rapidlynear TN; no decoupling is observed in LF up to 0.4T. In the ordered state we see a Lorentzian Kubo-Toyabe GZZ(t), becoming nearly static at the lowest temperatures. Its static width is very narrow (Δ≈-7 MHz), and full dceoupling is
achieved here in 0.1 T. On approaching TN, the fluctuation rate and the static width increase mootonically bt the field distribution remains Loratzian. A LF of 0.4T
is then insufficient to quench the fast exponential relaxation. In paramagnetic am-DyAg, the μ+ depolarization is always much faster then in cr-DyAg. At lower temperatures it is better described by a root-exponential
than an exponential GZZ(t). Below TC an exponentially relaxing signal with 1/3 amplitude is seen. The decoupling effect of LF up to 0.4T was negligible at all
temperatures. |
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