Abstract
Long-wavelength spin spiral structures are ubiquitous in a large variety of magnetic materials. The detailed magnetic structure can take many variations owing to their different physical origins. Therefore, the unambiguous structural determination is crucial for understanding these spin systems, though such a task is experimentally challenging. Here, we show that ordered spin spiral structures can be fully determined in a single measurement by dichroic resonant elastic x-ray scattering using circularly polarized light. It is found that at certain geometrical conditions, the circular dichroism of the diffraction vanishes completely, revealing a one-to-one correspondence with the spin structure. We demonstrate both theoretically and experimentally this experimental principle, which allows for unambiguous structure determination immediately from the measured signal, whereby no modeling-based data refinement is needed. This largely expands the capabilities of conventional magnetic characterization techniques.
Highlights
Spin spiral order is a general type of long-range magnetic order, which can be found in many materials systems
We have demonstrated a magneto-optical principle by combining resonant x-ray scattering and circular dichroism
Our measurement strategy requires that the incommensurate magnetic propagation wave vector lies within the x-y plane, which is probed as magnetic satellite peaks that decorate a structural peak
Summary
Spin spiral order is a general type of long-range magnetic order, which can be found in many materials systems. In patterned ferromagnetic stripes, DREXS measured by comparing the difference in diffracted intensity between left- and rightcircularly polarized incident x rays, reveals the chirality of the spin domain structure [38] It was demonstrated using a full polarization analysis of the scattered beam that for multiferroic TbMnO3 the circularly polarized x rays are sensitive to the handedness of the cycloidal-type spin spiral order [40]. We demonstrate both theoretically and experimentally that for an arbitrary spin helix, the DREXS surprisingly vanishes at certain geometrical conditions, which are specific signatures of a particular spiral structure We summarize this phenomenon as the dichroism extinction effect, which can be applied to unambiguously determine the detailed structure of chiral magnetic order, inaccessible to any other methods.
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