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تسجيل مستخدم جديدStrong $(pi,0)$ spin fluctuations in $beta$-FeSe observed by neutron spectroscopy
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We have performed powder inelastic neutron scattering measurements on the unconventional superconductor $beta$-FeSe ($T_{rm c} simeq 8,mathrm{K}$). The spectra reveal highly dispersive paramagnetic fluctuations emerging from the square-lattice wave vector $(pi,0)$ extending beyond 80 meV in energy. Measurements as a function of temperature at an energy of $sim 13,mathrm{meV}$ did not show any variation from $T_{rm c}$ to $104,mathrm{K}$. The results show that FeSe is close to an instability towards $(pi,0)$ antiferromagnetism characteristic of the parent phases of the high-$T_{rm c}$ iron arsenide superconductors, and that the iron paramagnetic moment is neither affected by the orthorhombic-to-tetragonal structural transition at $T_{rm s} simeq 90,mathrm{K}$ nor does it undergo a change in spin state over the temperature range studied.
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