Precise measurement of acoustic phonons in PrFeAsO

Fukuda, Tatsuo  ; Baron, A. Q. R.*; Uchiyama, Hiroshi*; Nakamura, Hiroki  ; Ishikado, Motoyuki*; Machida, Masahiko  ; Shamoto, Shinichi  

Using inelastic X-ray scattering (IXS), we investigated acoustic phonons of PrFeAsO precisely in order to select between two different models based on first principles calculations: the in-plane soft and clipped model. These models predict slightly different phonon intensities, and, in particular, different contamination of the longitudinal acoustic (LA) phonon spectra by transverse acoustic (TA) phonon modes. We were able to reduce the contamination with improved resolution, but the data quality was not sufficient to clearly decide between our models. Based on dependence there appears to be slightly better agreement with the in-plane soft model at room temperature.