Investigating the vibrational lattice anisotropy in FeTe0.5Se0.5 using magnetically oriented crystallites

Abstract

An iron chalcogenide sample with nominal composition FeTe0.5Se0.5 was synthesized following a solid-state reaction route. X-ray diffraction followed by Rietveld analysis were used for verifying the phase content. Using the field of an 11.7 T magnet textured samples, having the c axes parallel with and normal to the sample surface, were made. 57Fe Mössbauer spectroscopy in transmission geometry was used for characterizing the hyperfine parameters of the iron site. Clear indications of vibrational anisotropy, i.e. the Goldanskii-Karyagin effect, were observed. Fitting spectral absorption with the Debye model yielded rather low Debye temperatures of 255(3) and 303(3) K, for samples texturized with the c axis parallel with and perpendicular to the Mössbauer γ beam, respectively. Also the second-order Doppler shift of the isomer shift data exhibited a similar, although weaker, anisotropy.