Determination of magnetostriction for spin-valve devices with 5.0 and 10.0 nm Permalloy layers

The objective of this study is to determine the extent of magnetostriction in spin valves. Spin valves were fabricated on a silicon substrate using dc magnetron sputter deposition techniques with the following structure: Ta-5.0/NiFe5.0 or (10.0)/CO1.0/Cu-3.0/Co-3.0/Ru-0.6/Co-2.0/FeMn10.0/Ta-5.0, where the subscripts denote the layer thickness in nanometers. The Permalloy composition used in these studies was Ni80Fe20. Spin valves were created in a serpentine shape to maximize the total magnetostriction (DeltaL/L) by increasing the device length per die area. Device widths of between I and 40 mum with lengths of 1000-40 000 mum were fabricated. Devices were subjected to an external magnetic field while a mechanical force was applied to the backside of the substrate. An increase in the anisotropy field H-k, is observed with increasing stress. This increase is observed for all devices tested but is more distinct for those containing the 5.0 nm Permalloy. Results show that maximum magnetostriction occurs abruptly at lower stress values for the 10.0 nm Permalloy while magnetostriction for the 5.0 nra Permalloy occurs gradually over a wider range of stress values. Magnetoresistance measurements also show an inverse relationship between applied stress and (DeltaR/R) performance. Magnetostriction analysis becomes critical as both device complexity and integration levels increase. (C) 2001 American Vacuum Society.