Site-specific magnetism in ferro(ferri)-magnetic crystals

Crystallography combined with resonant scattering of circularly polarized (CP) x-rays can extract site-specific magnetism in crystals. Nd2Fe14B permanent magnet has two inequivalent Nd sites. Crystal symmetry results in structure factors probing either the 4ƒ or 4g sites at (220) and (110) Bragg reflections, respectively. Resonant diffraction at the Nd L2 edge (left panel) allows for Nd site-specific hysteresis loops (right panel) by monitoring the dichroism in diffracted intensity for opposite helicities of CP x-rays versus applield field. XMCD gives the site-averaged magnetization reversal. The Nd 4g sites appear to be responsible for the magnetic hardness of this material. [IEEE Trans. Mag., 40, 2874 (2004)).

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