Influence on the magnetoresistance of a spin valve due to the insertion of an ultrathin Gd layer in the free layer.

The effect of inserting an ultrathin Gd layer (1–2 nm) in the free layer of a Permalloy-based spin valve has been investigated. In the current in-plane configuration, samples with Gd show a reduced magnetoresistance (MR) value, which tends to zero as Gd gets closer to the nonmagnetic spacer, although good MR values can be sustained when Gd is more than 5 nm away from the spacer. We studied also the effect of adding thin Fe layers around Gd in order to avoid Gd diffusion within the Permalloy. Samples with an Fe/Gd/Fe trilayer inserted in the free layer show some improvement at low temperatures over those without Fe, although the Fe introduces some detrimental additional roughness. [ABSTRACT FROM AUTHOR]