Annealing Effect on Crystalline Structure of Current Screen Layer for CPP-GMR

We investigated the effects of annealing on crystalline structures in the current screen layer for current-perpendicular-to-plane giant-magnetoresistive (CPP-GMR) films. The current screen layer of an oxidized CoFe had a crystalline structure. The thickness of current screen layer that had not been annealed was uniform, even though the current screen layer was deeply wavy. On the other hand, the current screen layers that had been annealed became smoother when the annealing temperature was high. This suggests that the current screen layer was reconstructed by annealing to reduce the surface energy at the interfaces. We also measured the transport properties of these CPP-GMR films to clarify the annealing effects on their crystalline structures. The resistance area product (RA) became smaller with increasing the annealing temperature. The magnetoresistance (MR) ratio had a maximum value of 6.2% at an RA of 1.2 Omegamum 2 when the annealing temperature was 320 degC. Calculations indicate that the results obtained are due to not only an enlarged pinhole area, but also reduced pinhole resistance