Effect of chemical ordering on 90° interlayer coupling in epitaxial Co-Fe/Cr/Co-Fe thin films

摘要

Interlayer exchange coupling (IEC) was studied in ferromagnetic binary alloy Co-Fe thin films through Cr spacer to investigate systematically, the effects of chemical compositions and the chemical ordering on the observation of 90° interlayer coupling in magnetic alloy based structures. The dominating 180° coupling with weak 90° coupling was observed at room temperature deposited Co_xFe_(1-x)/Cr/Co_xFe_(1-x) (x=0 to 0.8) trilayer samples for all values of x. However, the strength of the 90° coupling for x=0.4 and 0.5 was found to increase with increasing the annealing temperature, T_(ann) for the bottom Co_xFe_(1-x) layer and the strength of 90° coupling became comparable to that of 180° coupling at T_(ann)=400℃. The enhancement of 90° coupling was considered to be originated from the unconventional interfacial magnetic exchange interactions between Cr and Co (and Fe) due to the appearance of antiphase structures at the interface with the enhancement of chemical ordering (B2 ordering) which was confirmed by synchrotron X-ray diffraction.