We present neutron diffraction analysis of BaFe2(As1−xPx)2 over a wide temperature (10 to 300 K) and compositional (0.11≤x≤0.79) range, including the normal state, the magnetically ordered state, and the superconducting state. The paramagnetic to spin-density wave and orthorhombic to tetragonal transitions are first order and coincident within the sensitivity of our measurements (∼0.5 K). Extrapolation of the orthorhombic order parameter down to zero suggests that structural quantum criticality cannot exist at compositions higher than x=0.28, which is much lower than values determined using other methods, but in good agreement with our observations of the actual phase stability range. The onset of spin-density wave order shows a stronger structural anomaly than the charge-doped system in the form of an enhancement of the c/a ratio below the transition.
@article{arxiv.1410.2630,
title = {Coincident structural and magnetic order in BaFe$_2$(As$_{1-x}$)P$_x$)$_2$ revealed by high-resolution neutron diffraction},
author = {Jared M. Allred and Keith M. Taddei and Daniel E. Bugaris and Sevda Avci and Duck Young Chung and Helmut Claus and Clarina dela Cruz and Mercouri G. Kanatzidis and Stephan Rosenkranz and Ray Osborn and Omar Chmaissem},
journal= {arXiv preprint arXiv:1410.2630},
year = {2014}
}