Close Correlation between Magnetic Properties and the Soft Phonon Mode of the Structural Transition in BaFe2A s2 and SrFe2As2

Published

April 27, 2015

Author(s)

Daniel E Parshall, L. Pintschovius, J. L. Niedziela, J.-P. Castellan, D. Lamago, R. Mittal, Th. Wolf, D. Reznik

Abstract

Parent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of transverse acoustic (TA) phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe₂As₂ and SrFe₂As₂. We found that acoustic phonons at small wavevectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuation magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.

Citation

Physical Review B

Volume

91

Issue

13

Pub Type

Journals

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Keywords

phonon, ferropnictide, magnetoelastic coupling

Citation

, D. , Pintschovius, L. , , J. , Castellan, J. , Lamago, D. , Mittal, R. , Wolf, T. and Reznik, D. (2015), Close Correlation between Magnetic Properties and the Soft Phonon Mode of the Structural Transition in BaFe₂A s₂ and SrFe₂As₂, Physical Review B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918242 (Accessed October 20, 2025)