INTERPLAY BETWEEN EXCHANGE BIASING AND INTERLAYER EXCHANGE COUPLING IN NI80FE20 CU/NI80FE20/FE50MN50 LAYER SYSTEMS/

Magnetoresistance curves have been measured for 80 angstrom Ni80Fe20/t (Cu) Cu/60 angstrom Ni80Fe20/80 angstrom Fe50Mn50 layered systems (t(C u) = 9-93 angstrom). After separating the contributions from anisotrop ic magnetoresistance and spin valve or ''giant'' magnetoresistance (GM R), the GMR curves were interpreted in terms of a minimum-energy model for the magnetization orientation of the Ni80Fe20 layers. The interla yer exchange coupling was found to be purely ferromagnetic, and monoto nically decreasing with increasing t(Cu). The interplay of this coupli ng with the exchange biasing effect results in a critical interlayer t hickness, t(Cu)crit = 15 angstrom, below which no perfect antiparallel alignment of the Ni80Fe20 magnetizations can be realized. The GMR, wh ich would otherwise increase with decreasing Cu layer thickness, is th erefore expected to reach a maximum at or slightly below t(Cu)crit. In deed, such a maximum was found (with DELTAR/R = 4.3 %) at t(Cu) = 22 a ngstrom, a value well above t(Cu)crit. This is attributed to the occur ence of inhomogeneities in the interlayer exchange coupling.