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Schematic (oblique side view) of the epitaxial trilayer film used in this experiment showing the orientation of the transverse SDW and accompanying CDW. The capped Cr layer on the left shows only one of two possible orthogonal orientations for the in-plane CDW. In the uncapped region of Cr, we expect a single out-of-plane orientation of the CDW following the removal of Fe.
X-ray scans along the (0,0,L) direction with an unfocused (200 ×200) μm2 beam. (a) Scans taken 400 µm into the uncapped Cr region. The 4 K data (top red curve) are displaced upward by 2000 cps for clarity. The top blue curve shows RT data. The background (dashed black line) has been fitted with the same Gaussian function for both curves. The bottom red and blue curves represent the 4 K and RT data, respectively, with the background subtracted. Background subtraction leaves only the out-of-plane (0,0,2-2δ) CDW intensity centered at 1.901 at 4 K (red) and around 1.923 at RT (blue). (b) Scans taken 400 µm into the capped Fe region. The oscillations observed at both temperatures are interference fringes due to the thickness of the Fe cap layer. The 4 K data (red curve) are displaced upward by 2000 cps for clarity. The blue curve shows data taken at RT. The dark green curve is the difference between 4 K and RT showing that the signal is temperature independent. There is no signal arising from an out-of-plane (0,0,2-2δ) charge-density wave on the Fe capped side.
(a) X-ray microdiffraction scan at 4 K across the Fe capped/uncapped boundary of the Cr film where positive (negative) distance corresponds to the distance from the domain wall into the uncapped (capped) side. Scan shows CDW intensity along the (0,0,L) direction after subtracting the temperature independent background. The increased signal around Q = 1.901 r.l.u in the uncapped side is expected for the out-of-plane CDW of chromium at 4 K. In the capped region, scans show no peak indicating that the CDW has rotated to lie in-plane. (b) Fe x-ray microfluorescence intensity (red curve) and summed CDW intensity (blue curve) across the capped/uncapped boundary. The black curve is the expected CDW intensity predicted from the unfocused beam data of Fig. 2.
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