The effect of Ta on the magnetic thickness of permalloy (Ni{sub 81}Fe{sub 19}) films
- Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
- Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
- Honeywell, Inc., MN14-3C15, 12001 State Highway 55, Plymouth, Minnesota 55441 (United States)
The effect of Ta and Ta/Cu seed layers, and Ta and Cu cap layers on the effective magnetic thickness of ultrathin permalloy (Ni{sub 81}Fe{sub 19}) was investigated for MRAM applications. The films were deposited by Ion Beam Deposition. The magnetic moment of each as-deposited permalloy film was measured using a B-H looper and a SQUID magnetometer. The films were further annealed at either 525 K for 1/2 h or 600 K for 1 h to study the effect of thermally driven interdiffusion on the magnetic moment of the permalloy film. Our theoretical calculations showed that the presence of 12% intermixing at the interface reduces the Ni moments to zero. Experimentally, it was shown that the tantalum rather than the copper interfaces are primarily responsible for the magnetically dead layers. The Ta seed layer interface produces a loss of moment equivalent to a magnetically dead layer of thickness 0.6{+-}0.2 nm. The Ta metal in the cap layer results in a loss of moment equivalent to a dead layer of thickness 1.0{+-}0.2 nm. Upon annealing, thermally driven interdiffusion is concluded to have a strong effect on the Ta(seed)/ Ni{sub 81}Fe{sub 19} as-deposited interface, based on the doubling of the magnetically dead layer to 1.2{+-}0.2 nm. The Ni{sub 81}Fe{sub 19}/Ta(cap) as-deposited interface slightly increases its equivalent magnetically dead layer upon annealing to 1.2{+-}0.2 nm. As-deposited interfaces of Ta(seed)/permalloy and permalloy/Ta(cap) are not chemically equivalent and result in different magnetically dead layers, whereas after annealing to 600 K both interfaces attain comparable intermixing and magnetically dead layers. It was also shown that a half-hour anneal at the lower 525 K annealing temperature, which is closer to the actual processing temperature, results in only slight increase of the magnetically dead layer at both interfaces. (c) 2000 American Institute of Physics.
- OSTI ID:
- 20216244
- Journal Information:
- Journal of Applied Physics, Vol. 87, Issue 9; Other Information: PBD: 1 May 2000; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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