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Structural and magnetic characterization of uncapped FeRh thin film. (a) Phi scan of the (101) FeRh peak showing the four fold symmetry characteristic of an epitaxial growth. (b) Magnetization hysteresis loops of the uncapped FeRh thin film as a function of temperature.
Effect of capping layer and temperature on FM domains in FeRh thin film. XMCD-PEEM asymmetry images (difference between right and left polarization images divided by their sum, in zero applied magnetic field) of FeRh thin films showing FM domains in the AF and FM states (temperature of image shown in upper left corner) for the film without capping layer (No cap (a) and (b)) and the film capped with 2.5 nm of Al (Al cap (c) and (d)). FM domains with a positive (negative) projection of the magnetization onto the x-ray beam direction are shown in different intensities of blue (red). The asymmetry colorscale used for the 4 images is shown in (a).
Temperature evolution of FM domains in the uncapped FeRh thin film, temperature hysteresis, and FM domain configuration. (a) to (e) show heating from AF to FM and (f) to (j) show cooling from FM to AF, in zero field. The asymmetry (difference between right and left polarization images divided by their sum) colorscale used for these images is from −0.15 to 0.15. Normalized M-T hysteresis measured at 5 T is shown in the upper panel of (k); the temperature axis has been corrected to zero field. Integrated absolute XMCD of a representative region of interest (ROI—shown in inset) as a function of temperature is shown in the lower panel of (k). The sample configuration with respect to the x-ray beam and the direction of the projection of the beam in the images are shown in (m). The distribution of asymmetry in (e) (415 K) is shown as a histogram in (n). The two maxima are assigned to two pairs of equivalent FeRh ⟨100⟩ in-plane directions as preferred orientation of FM domains (easy axis). The four ⟨100⟩ directions are sketched in (p).
(a) Temperature evolution of absolute asymmetry of 4 different local areas (6 pixels × 6 pixels) showing the sharp local increase in magnetic contrast at the single domain nucleus scale and the spread of the nucleation regime over about 25 K. The location of the nuclei is indicated in the inset (XMCD-PEEM asymmetry image at 372 K). While islands initially nucleate as single domains, they then break into several domains upon increasing size. (b) An enlargement of the XMCD-PEEM image from Fig. 3(b) taken at 364 K showing FM nuclei in AF matrix in an uncapped FeRh thin film. Several nuclei with diameter of 200 nm or above are indicated by dotted circles and show flux closure patterns as seen by red and blue lobes.
XMCD-PEEM asymmetry images showing the transition from nucleation regime to growth regime in FeRh thin film between 379 K (same as Fig. 3(c)) and 396 K (same as Fig. 3(d)). The coalescence of FM domains is seen between (b) 384 K and (c) 391 K.
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