Domain analysis in epitaxial iron-aluminum and iron-gold sandwiches with oscillatory exchange

Epitaxially grown iron-iron sandwiches with wedge-shaped gold and aluminum interlayers are investigated by Kerr microscopy. While in the Fe-Au-Fe sample an oscillatory exchange (which appears, however, of a rather weak and irregular nature) interaction is confirmed, only one transition from ferromagnetic to 90°-coupling is found in the Fe-Al-Fe sample. For Al thickness >15 Å, the domains assume an irregular character, indicating an essentially uncoupled nature. This finding is confirmed by a new technique based on the magnetooptical Voigt effect observed at perpendicular incidence