Magnetic coupling in asymmetric FeCoV/Ru/FeNi trilayers.

We have investigated the magnetic anisotropy and interlayer coupling in trilayer films of permendur(100Å )/Ru/permalloy(100Å ), with the thickness of the Ru spacer varying from 0 to 200Å . While the permendur/permalloy sample exhibits a small in-plane uniaxial magnetic anisotropy with H_u=27 Oe, all trilayers are magnetically isotropic in-plane. Results from hysteresis loop and ferromagnetic resonance measurements were fitted to a micromagnetic model, with the results indicating that all the films are ferromagnetically coupled except the one with 10Å Ru spacer, which shows antiferromagnetic coupling. The trilayers with Ru spacer layer thickness larger than 20Å exhibit only very weak ferromagnetic coupling. [ABSTRACT FROM AUTHOR]