Enhancement of magnetoresistance with low interlayer coupling by insertion of a nano-oxide layer into a free magnetic layer

Abstract

We studied the interlayer coupling strength (H-in) and GMR ratio of a spin-valve with the top free layer, separated by a nano-oxide layer (NOL). With the total thickness of the top free layer being fixed at 60 A, the physical properties of the NOL spin-valve were studied with the thickness (t(f)) of the free layer under the inserted NOL and compared with those of the normal spin-valve with the same thickness as tf. It was found that the spin-valve with NOL has a higher GMR ratio than that of the normal spin-valve at the optimal condition (t(f)=40 angstrom) after thermal annealing at T=250 degrees C. The NOL spin-valve also shows a lower H-in than that of the optimal normal spin-valve with t(f)=40 angstrom, which is comparable to that of the normal spin-valve with t(f)=60 angstrom. This indicates that the enhancement of GMR, while keeping the Hin to be low, can be achieved by inserting a NOL into the top free layer. (c) 2005 American Institute of Physics.