Effect of corrosion on magnetic properties for FeMn and NiO spin valves

Abstract

Spin-valve multilayer structures are promising candidates for next generation read heads in high-density magnetic recording applications. Two commonly used antiferromagnetic layers that exhibit effective pinning for spin valves are FeMn and NiO. Previously, the only corrosion studied of the two materials with respect to magnetic recording are concerned with immersing thin films into acidic and basic solutions. In a realistic corrosion study of spin valves constructed with these pinning materials, we find a high humidity environment is catastrophic to the FeMn spin valves, even with protective Ta capping layers. Scanning electron microscopy along with magnetic measurements on edge protected samples gives convincing evidence that edge effects seem to dominate. Protection of the edges with an epoxy film merely slows down the degradation. In contrast, NiO spin valves show remarkable resistance to corrosion. While magnetoresistance ratio decreases for FeMn spin valves with increased corrosion, coercivity remains relatively constant and pinning field actually increases for both material systems.