Neutron Powder Diffraction Study on the Non-Superconducting Phases of ThFeAsN1−xOx (x = 0.15, 0.6) Iron Pnictide**Supported by the Strategic Priority Research Program of Chinese Academy of Sciences under Grant Nos XDB07020300 and XDB25000000, the National Key Research and Development Program of China under Grant Nos 2017YFA0303103, 2017YFA0302903 and 2016YFA0300502, the National Natural Science Foundation of China under Grant Nos 11374011,

Abstract

We use neutron powder diffraction to study the non-superconducting phases of ThFeAsN1−xOx with x = 0.15, 0.6. In our previous results of the superconducting phase ThFeAsN with Tc = 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 ThFeAsN1−xOx, 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.