X-ray Microdiffraction Images of Antiferromagnetic Domain Evolution in Chromium

Magnetic x-ray diffraction combined with x-ray focusing optics is used to image individual antiferromagnetic spin density wave domains in a chromium single crystal at the micron scale. The cross section for non-resonant magnetic x-ray scattering depends on the antiferromagnetic modulation vector and spin polarization direction and allows these quantities to be extracted independently. The technique is used to show that the broadening of the nominally first order "spin-flip" transition at 123 K, at which the spins rotate by 90 deg., originates at the walls between domains with orthogonal modulation vectors. During cooling the transition begins at these walls and progresses inwards. The modulation-vector domains are themselves unchanged.