New experimental evidence for spin fluctuations in strongly paramagnetic alloys

E. Fawcett, E. Bucher, W. F. Brinkman, J. P. Maita, J. H. Wernick

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According to theoretical predictions, the entropy of spin fluctuations in a paramagnetic metal with Stoner susceptibility enhancement factor S is (omitting numerical coefficients) ΔS/S0≃lnS+S3T 2ln (T/Ts), where S0 is the entropy of the electrons without spin fluctuations and Ts=TFermi/S. The first term gives rise to an enhancement of the specific heat and the thermal expansion at absolute zero. The second term should cause a low-temperature anomaly in both properties. The enhancement of the specific heat has been reported in NiRh and Pd:Ni alloys, and the NiRh system also shows low-temperature specific-heat anomalies. The thermal expansion α is more sensitive than the specific heat C to each of these contributions, approximately in the ratio Δα/α0/ΔCv/C v0≃1/ γ0∂lnS/∂lnV, where γ0 is the electronic Gruneisen parameter without spin fluctuations. Our magnetostriction data for Pd:Ni and NiRh alloys determines ∂ lnS/∂ lnV, which is proportional to S in accordance with the Stoner expression for the susceptibility. The thermal expansion of the Pd:Ni alloys as temperature approaches zero shows the expected enhancement, and the most strongly enhanced sample shows a low-temperature anomaly. The low-temperature thermal expansion of the NiRh alloys in general increases with Ni concentration, but the behavior is complicated by clustering effects. The ordered intermetallic compound Ni3Ga is found to have a large magnetostriction corresponding to its strong exchange enhancement, but as for the disordered alloys, the low-temperature anomaly in its thermal expansion depends upon the annealing treatment.

Original languageEnglish (US)
Pages (from-to)1097-1098
Number of pages2
JournalJournal of Applied Physics
Issue number3
StatePublished - 1969

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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