Abstract
We use neutron diffraction to study the temperature evolution of the average structure and local lattice distortions in insulating and superconducting potassium iron selenide . In the high temperature paramagnetic state, both materials have a single phase with a crystal structure similar to that of the BaFeAs family of iron pnictides. While the insulating forms a iron vacancy ordered block antiferromagnetic (AF) structure at low temperature, the superconducting compounds spontaneously phase separate into an insulating part with iron vacancy order and a superconducting phase with chemical composition of KFeSe and BaFeAs structure. Therefore, superconductivity in alkaline iron selenides arises from alkali deficient KFeSe in the matrix of the insulating block AF phase.
- Received 4 March 2014
- Revised 3 April 2014
DOI:https://doi.org/10.1103/PhysRevB.89.134509
©2014 American Physical Society