Dzyaloshinskii--Moriya interaction: How to measure its sign in weak ferromagnetics?

Three experimental techniques sensitive to the sign of the Dzyaloshinskii--Moriya interaction are discussed: neutron diffraction, Moessbauer gamma-ray diffraction, and resonant x-ray scattering. Classical examples of hematite (alpha-Fe2O3) and MnCO3 crystals are considered in detailComment: 5 pages, 1 figure; to be published in JETP Letter

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Abstract -Experimental results are presented on the measurement of a holographic (phase-contrast) image of a boric fiber (100-µ m-diameter boric cylinder with a 20-µ m-diameter tungsten core) and on radiation focusing by Fresnel zone plates using the Kurchatov synchrotron radiation source. By comparison of the obtained hologram with theoretically calculated data, the vertical size of the source was determined to be 325 ± 25 µ m. This value was also confirmed by measuring the half-width of the direct image of the source. Features of image recording on a photographic film are discussed