科研之友
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摘要
Ba2Ti2Fe2As4O is a self-doped superconductor exhibiting a Tc similar to 21.5K and containing, distinctively with respect to other Fe-based superconductors, not only [Fe2As2] layers but also conducting [Ti2O] sheets. This compound exhibits a transition at T* similar to 125 K, which has tentatively been assigned in the literature to a possible density-wave order. However, the nature of this density wave (whether it is charge-or spin-induced) is still under debate. Magnetism in Ba2Ti2Fe2As4O has never been experimentally confirmed, which raises the question whether this superconductor might be nonmagnetic or exhibiting a very weak magnetism. Here, we report evidence from inelastic neutron scattering (INS) measurements and ab initio calculations of phonon spectra pointing towards a possible absence of magnetism in Ba2Ti2Fe2As4O. The INS measurements did not reveal any noticeable magnetic effects in Ba2Ti2Fe2As4O, within the accessible (Q, E) space. The effect of magnetism on describing phonon spectra was further investigated by performing ab initio calculations. In this context, nonmagnetic calculations reproduced well the measured phonon spectra. Therefore, our results indicate a nonmagnetic character of the superconductor Ba2Ti2Fe2As4O.
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