Figure 2

Magnetic fluctuation spectra in the AFM and SC states at various l values. (a) Sketch of the three orthogonal directions with respect to the ordered Fe moment. (b) Geometrical conditions for polarized INS at (0.5, 0.5, l) with respect to the spin-space anisotropy. (c–e) Polarized INS intensity at (0.5, 0.5, l) with l = 1, 3 and 5 in the different spin-flip (SF) channels after subtracting the background and correcting for the Bose and form factors. These data correspond to the dynamical susceptibilities χ″ multiplied with the geometry factors and folded with resolution function. The nine curves are consistently fitted (lines) by the three susceptibilities \({\chi^{\prime\prime}}_{long}\), \({\chi^{\prime\prime}}_{t-in}\) and \({\chi^{\prime\prime}}_{t-out}\) each described by a single log-normal distribution. These individual susceptibilities are resumed in (f); their amplitude follows an 1/E relation. A fit with a single relaxor function is not possible, as indicated by the dotted line in (c). (g–i) The same data in the SC phase at 1.5 K, where only two additional resonance components in \({\chi^{\prime\prime}}_{t-in}\) and \({\chi^{\prime\prime}}_{t-out}\) are needed to again consistently describe all nine curves. These additional resonance contributions are shown in (j), where dashed lines denote the anisotropic response in the normal state (same as in (f)).