AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Paper MI-ThA1
The Determination of Magnetostriction for Spin-Valve Devices with 5.0 nm and 10.0 nm Permalloy Layers

Thursday, October 5, 2000, 2:00 pm, Room 206

Session: Magnetic Devices: GMR & Tunneling
Presenter: T.J. Gafron, Boise State University
Authors: T.J. Gafron, Boise State University
S.E. Russek, National Institute of Standards and Technology
S.L. Burkett, Boise State University
Correspondent: Click to Email
The objective of this study is to determine the extent of magnetostriction in spin-valves. Spin-Valves were constructed on a silicon substrate using dc magnetron sputter deposition techniques with the following structure: Ta@sub 5.0@ /NiFe@sub 5.0 or 10.0@ /Co@sub 1.0@ /Cu@sub 3.0@ /C0@sub 3.0@ /Ru@sub 0.6@ /Co@sub 2.0@ /FeMn@sub 10.0@ /Ta@sub 5.0@, where the subscripts denote the layer thickness in nanometers. The films were deposited with a magnetic field applied parallel to the substrate to align the pinned and free layers. Spin-valves were designed in a serpentine shape to maximize magnetostriction effects by increasing the device length. Device widths between 1 and 40 microns and lengths between 100 and 2000 squares were fabricated. Spin-valves tested exhibited a 5-7% change in magnetoresistance and an average ferromagnetic exchange coupling of 0.4 kA/m at 300°K. Devices were subjected to an external magnetic field while a mechanical stress was applied to the backside of the substrate. A four-point probe technique was used to measure device resistance as a function of applied field and mechanical stress. An increase in the anisotropy field, H@sub k@, is observed with increasing mechanical stress. This increase is observed for all devices tested but more distinct for those containing the 5.0 nm Permalloy. Using the curvature of the stressed sample and the thickness of the spin-valve and substrate, magnetostriction is calculated as a function of the applied stress. Results show that maximum magnetostriction occurs abruptly at lower stress values for the 10.0 nm Permalloy while magnetostriction for the 5.0 nm permalloy occurs gradually over a wider range of stress values. Magnetostriction is small (1.50 microns for the 20 micron by 1K square, 5.0 nm NiFe), but the effect is pronounced and impacts device performance as demonstrated by a shift in H@sub k@. Magnetostriction analysis becomes critical as both device complexity and integration levels increase.