Probing the phase transition of methane with Mössbauer effect in 57Fe impurities

M. Pasternak*, P. H. Barrett

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Mossbauer studies were performed in 57Fe impurities (0.3% at.) in solid methane, in order to investigate the properties of the order-disorder phase transition taking place at Tc=20.4K. From the temperature dependence of the relative values of the recoil-free-fraction - f - it was found that near Tc a change occurs in the slope of f(T2) without discontinuity in the value of f. A consistent model is proposed by which immediately below Tc both phases, I and II coexist with a gradual evolution of the ordered state (II) on the account of the high temperature plastic state (I). The Debye temperature of phase II (θII = 101±7K) increases with respect to that of phase I (θI = 72±3K), indicating a hardening in the phonon spectrum and precluding the onset of rotational modes of the disordered molecules.

Original languageEnglish
Pages (from-to)771-774
Number of pages4
JournalSolid State Communications
Volume27
Issue number8
DOIs
StatePublished - Aug 1978

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