Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition
The surface magnetic domain structure of uncapped epitaxial FeRh/ MgO(001) thin films was imaged by in-situ scanning electron microscopy with polarization analysis (SEMPA) at various temperatures between 122 and 450 K. This temperature range covers the temperature-driven antiferromagnetic-to-ferromagnetic phase transition
in the body of the films that was observed in-situ by means of the more depth-sensitive magneto-optical Kerr eff ect.
The SEMPA images confirm that the interfacial ferromagnetism coexisting with the antiferromagnetic phase inside the film is an intrinsic property of the FeRh(001) surface. Furthermore, the SEMPA data display a reduction of the in-plane magnetization occuring well above the phase transition temperature which, thus, is not related to the volume expansion at the phase transition.
This observation is interpreted as a spin reorientation of the surface magnetization for which we propose a possible mechanism based on temperature-dependent tetragonal distortion due to diff erent thermal expansion coefficients of MgO and FeRh.
Figure: (a-h) SEMPA domain images of an uncapped 10 nm thick FeRh(001) film on MgO(001) measured in zero field and at different temperatures as indicated. Images are taken in the sequence (a) to (h) and show the same sample area: Black circles mark the same features. (i) Color-wheel for the representation of the in-plane spin asymmetry vectors A(x, y) = (Ax, Ay) and scale bar for all images.
Xianzhong Zhou, Frank Matthes, Daniel E. Bürgler, and Claus M. Schneider
Magnetic surface domain imaging of uncapped epitaxial FeRh(001) thin films across the temperature-induced metamagnetic transition
AIP Advances 6, 015211 (2016)