Concerning the two magnetic correlation lengths above T
c
in an Invar iron-nickel alloy |
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| Authors: | S V Grigor’ev S A Klimko S V Maleev A I Okorokov V V Runov R Kampmann H Eckerlebe |
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| Institution: | (1) St. Petersburg Institute of Nuclear Physics, Russian Academy of Sciences, 188350 Gatchina, St. Petersburg, Russia;(2) GKSS Forschungszentrum, 21502 Geesthacht, Germany |
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| Abstract: | The magnetic phase transition in the Invar alloy Fe70Ni30 is investigated by means of small-angle neutron scattering over a wide range of momentum transfer. This method was used to
measure two magnetic correlation lengths R
c
1 and R
c
2 which coexist in the alloy above the phase transition temperature T
c
. The critical correlations with correlation length R
c
1 are described well by an Ornstein-Zernicke expression, and the critical correlations with the second correlation length,
an order of magnitude larger than R
c
2, are described well by a squared Ornstein-Zernicke expression. The temperature dependences obtained for the correlation
lengths R
c
1 and R
c
2 satisfy the power law R
c
∼((T−T
c
)/T
c
) −υ with critical exponents υ1=0.65±0.05 and υ2=1.3±0.1 for the shorter and longer scales, respectively.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 53–57 (10 July 1997) |
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| Keywords: | |
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