Progress of a GMR element by the simulation of film formation process and microfabrication

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The recording density of HDDs rises at an annual rate of 80 to 100 %. The giant magnetoresistance (GMR) effect in Co/Cu multilayers is one of the important issues for achieving high sensitive magnetic head. It is known that current-perpendicular-to-the-plane (CPP) GMR shows higher MR ratios than current-in-plane (CIP) GMR. It is commonly known that GMR effect depends on the nanostructure at the interface in the superlattice.(1) For the purpose of clarifying the nanostructure at the surface during the film formation process, we performed molecular dynamics (MD) simulations for the Cu deposition behavior on aCu (111) single crystal substrate. After the deposition of 0.6 Cu atoms monolayer on a single crystal substrate, [ABC] and [AB/A] structures were observed at the surface. With increasing thickness of the deposited layer, [ABC] and [AB/A] structures contacted each other, and stacking faults appeared inside the third deposited layer. Then the grain structure appeared inside the fourth deposited layer merely over the area where the stacking faults were observed inside the third deposited layer. Then, the dependence of the interface structure to the kinetic energies of incident atoms derived from simulations corresponds well to the experimental results of NMR spectram.(2) We performed micro fabrication of Co/Cu multilayers using a focused ion beam (FIB) etching machine to increase MR ratios by changing the current flow path. Ga contamination of the specimen caused by FIB processing was within 3 nm. As a result, the MR ratio increased from 4.55 % to 8.90%.