Chiral spin spiral in synthetic antiferromagnets probed by circular dichroism in x-ray resonant magnetic scattering

Noncollinear chiral spin textures in ferromagnetic multilayers are at the forefront of recent research in nanomagnetism with the promise of fast and energy-efficient devices. The recently demonstrated possibilities to stabilize such chiral structures in synthetic antiferromagnets (SAFs) has raised interest as they are immune to dipolar field, hence favoring the stabilization of ultrasmall textures. They also improve mobility and avoid the transverse deflections of moving skyrmions limiting the efficiency in some foreseen applications. However, such systems with zero net magnetization are difficult to characterize by most of the standard techniques. Here, we report that the relevant parameters of a magnetic SAF texture, those being its period, its type (N\'eel or Bloch), and its chirality (clockwise or counterclockwise), can be directly determined using the circular dichroism in x-ray resonant scattering at half-integer multilayer Bragg peaks in reciprocal space. The analysis of the dependence in temperature down to 40 K allows us moreover to address the question of the temperature stability of a spin spiral in a SAF sample and of the temperature scaling of the symmetric and antisymmetric exchange interactions.