Ferro- and antiferromagnetic exchange coupling in magnetooptical bilayers with planar and perpendicular anisotropy

Macroscopic ferro- (F) and antiferromagnetic (AF) exchange couplings -A/sub 12/M/sub 1/.M/sub 2/ between a planar GdFeCo film 1 and a perpendicular anisotropy DyFeCo film 2 have been investigated from the magnetization processes of the bilayer as observed from Faraday rotation measurements. Whatever the F or AF coupling, the microscopic exchange interaction between the rare-earths and the transition metals at the interface induces mutual effects with a reduction of the coercivity H/sub C2/ and the squareness M/sub r2//M/sub s2/ of the "perpendicular" layer and a reduction of the saturation field H/sub s1/, but an increase of the coercivity H/sub C1/ of the planar layer. Experiments performed in single planar and perpendicular layers and in both pseudo F and AF bilayers are in agreement with our theoretical model which enables deduction of the macroscopic exchange constant A/sub 12/.