Aging in Thin Metallic Films.
NAVAL SURFACE WEAPONS CENTER WHITE OAK LAB SILVER SPRING MD
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Low magnetostriction NiFe and NiFe based ternary films 220A and 340A thick were prepared by thermal evaporation and bias sputtering. A few evaporated films were sputter etched. The films were aged in air with a magnetic bias in the plane of the film and perpendicular or parallel to the easy axis. Changes in uniaxial anisotropy field, coercive force and magnetostriction were measured as a function of time at temperatures of 100 C to 225 C. Films aged below 125 C in easy axis fields had an activation energy of 0.75ev in the case of evaporated NiFe while no change was observed in the case of sputtered or sputter etched NiFe or for a ternary Ni-Fe-Au. All films responded to temperatures above 125 C with activation energies of 1.3 to 2.4 ev. The rate of response was 50 to 1000 times greater in evaporated NiFe than in the other films. All films stored at 150 C in a hard axis field showed a large decrease in anisotropy field. The rate of change was dependent on deposition conditions and annealing temperature. Sputter etching was capable of reorienting the anisotropy axis. Author
- Metallurgy and Metallography