%0 Journal Article
%A Mittal, R.
%A Heid, R.
%A Bosak, A.
%A Forrest, T.R.
%A Chaplot, S.L.
%A Lamago, D.
%A Reznik, D.
%A Bohnen, K.P.
%A Su, Y.
%A Kumar, C. M. N.
%A Dhar, S.K.
%A Thamizhavel, A.
%A Rueegg, Ch.
%A Krisch, M.
%A McMorrow, D.F.
%A Brückel, T.
%A Pintschovius, L.
%T Pressure dependence of phonon modes across the tetragonal to collapsed tetragonal phase transition in CaFe2As2
%J Physical review / B
%V 81
%N 14
%@ 1098-0121
%C College Park, Md.
%I APS
%M PreJuSER-9354
%P 144502
%D 2010
%Z Record converted from VDB: 12.11.2012
%X The pressure dependence of a large number of phonon modes in CaFe2As2 with energies covering the full range of the phonon spectrum has been studied using inelastic x-ray and neutron scatterings. The pressure range was large enough to cover the first-order phase transition into the so-called collapsed phase where the c-axis contracts by about 6% whereas a and b axes expand by about 1.5%. Our main result is that pressure-induced phonon frequency shifts are well explained by the changes in relevant bond lengths throughout the pressure range, including those associated with the first-order phase transition. Specifically, the frequencies of phonons polarized in the ab plane as well as the Fe-As bond lengths change little across the phase transition. On the other hand, the transverse-acoustic phonons propagating along the c direction stiffen very significantly in response to the large contraction of the bonds along the c axis. Nonmagnetic density-functional calculations describe the frequencies in both the zero pressure and in the collapsed phase in a satisfactory way if based on the respective experimental crystal structures. This suggests that there is no need to invoke changes in magnetic moments on Fe atoms to explain the pressure-induced frequency shifts.
%K J (WoSType)
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000277210200098
%R 10.1103/PhysRevB.81.144502
%U https://juser.fz-juelich.de/record/9354