Figure 1

(a) The SDW (thin arrows normal to both [111] and $\mathit{\tau }$) produced by the tilt of the Fe spins out of the plane of the magnetic cycloid (thick arrows in the plane defined by [111] and $\mathit{\tau }$). The amplitude of the SDW is exaggerated. Only a few representative spins are shown. Open arrows show local magnetization due to the SDW. (b) and (c): Images of the diffraction pattern in the (111) scattering plane with (b) unpolarized neutrons, (c) neutrons polarized with $\mathbf{P}\parallel$ beam that scatter with spin flip. The images were prepared by summing several detector measurements over a range of rocking angles $\beta$ (see text), allowing all Bragg reflections from the long-wavelength modulation to be presented in a single image. A beam stop blocks the direct beam in the center of each image.Reuse & Permissions

Figure 2

Details of the $\pm {\mathit{\tau }}_1$ diffraction spots [left and right spots in Figs. 1b, 1c], using neutrons polarized with $\mathbf{P}\parallel$ beam. Corrections for the polarizing efficiency of the instrument have been included. (a) $|\mathbf{q}|$ dependence of azimuthally averaged intensity through both left and right spots at the peaks of their rocking curves. The solid line depicts a Gaussian fit. (b) and (c): Rocking curves for both left and right spots in the SF (b) and NSF (c) channels. The solid lines are Lorentzian fits. The dashed and dotted bars in these figures illustrate aspects of the experimental resolution discussed in the text. 55°-wide sectors on the detector were used to pick out the $\pm {\mathit{\tau }}_1$ spots; similar results may be obtained with smaller sectors and/or by examining another pair of diffraction spots $\pm {\mathit{\tau }}_2$, $\pm {\mathit{\tau }}_3$.Reuse & Permissions

Figure 3

Data for neutrons polarized with $\mathbf{P}\perp$ beam, in the vertical direction on the detector. (a) Schematic in detector plane illustrating the relationship between $\mathbf{P}$, $\mathit{\tau }$, and the components ($X$, $Y$, $Z$) of the vector $\mathbf{T}$ associated with the magnetic modulation. (b) Dependence on the angle $\alpha$ between $\mathit{\tau }$ and $\mathbf{P}$ of the polarized neutron intensities for all Bragg spots $\pm {\mathit{\tau }}_i$, each integrated over its rocking curve and normalized by its relative domain population. Both the SF and NSF channels are shown. The lines are fits described in the text.Reuse & Permissions