Neutron Powder Diffraction Study on the Non-Superconducting Phases of ThFeAsN1−xOx (x = 0.15, 0.6) Iron Pnictide*

Abstract

We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN 1−x O x with x = 0.15, 0.6. In our previous results of the superconducting phase ThFeAsN with T c = 30 K, no magnetic transition is observed by cooling down to 6 K, and possible oxygen occupancy at the nitrogen site is shown in the refinement [Europhys. Lett. 117 (2017) 57005]. Here in the oxygen doped system ThFeAsN 1−x Ox, two superconducting regions (0 ⩽ x ⩽ 0.1 and 0.25 ⩽ x ⩽ 0.55) are identified by transport experiments [J. Phys.: Condens. Matter 30 (2018) 255602]. However, within the resolution of our neutron powder diffraction experiment, neither the intermediate doping x = 0.15 nor the heavily overdoped compound x = 0.6 shows any magnetic order from 300 K to 4 K. Therefore, while it shares the common phenomenon of two superconducting domes as most 1111-type iron-based superconductors, the magnetically ordered parent compound may not exist in this nitride family.