using neutron diffraction at the australian centre for neutron scattering, researchers have been able to clarify the absence of magnetic order and classify the superconductivity of next-generation superconductors, such as thfeasn (an iron-based nitride).

the study examined superconducting materials. (wikimedia commons)

according to a report from the australian nuclear science and technology organization (ansto), scientists from the beijing national laboratory for condensed matter physics collected diffraction measurements to determine the crystal structure of the compound over a range of temperatures.

“in similar types of materials,” the report explained, “the onset of a superconducting state is thought to be associated with magnetic ordering within the crystal structure. earlier measurements had shown no magnetic ordering in the thfeasn material, and hence this neutron study was an opportunity to confirm this and search for other structural insights into the material’s properties.”

the study confirmed the lack of magnetic order and studies of the diffraction patterns from 6°k to 300°k also showed no structural phase transition from tetragonal to orthorhombic in the lattice.

“the investigators reported that the lattice parameters continuously increased with temperature due to thermal expansion and a weak distortion in the tetrahedron possibly took place at 160 k,” the article added. “details from the structure point to this distortion coming from the feas₂ layers.”

the results of the study indicate that, unlike other superconducting materials, thefeasn is in a “nearly optimized superconducting state.”

“the authors also surmised that the close distance of fe-as would favor electron hopping, reducing electron correlations and orbital order, thereby providing a reasonable explanation for the absence of magnetic order, structural transition and resistivity anomaly,” the article concluded.

the research was recently published in europhysics letters. the abstract read:

“we report neutron diffraction and transport results on the newly discovered superconducting nitride thfeasn with . no magnetic transition, but a weak structural distortion around 160 k, is observed by cooling from 300 k to 6 k.

“analysis on the resistivity, hall transport and crystal structure suggests that this material behaves as an electron optimally doped pnictide superconductor due to extra electrons from nitrogen deficiency or oxygen occupancy at the nitrogen site, which, together with the low arsenic height, may enhance the electron itinerancy and reduce the electron correlations, thus suppressing the static magnetic order.”