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Title: Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films

Abstract

Thin film CoPt/Co bilayers have been prepared as a model system to investigate the relationship between microstructure and exchange coupling in two-phase nanocomposite permanent magnets. The bilayers were prepared by magnetron sputter deposition of near-equiatomic CoPt with a thickness of 25 nm onto oxidized Si wafers. In the as-deposited state, CoPt had the A1 (fcc) structure and was magnetically soft. Before reinsertion into the sputtering chamber for the deposition of 2.8-16.7 nm thick Co layers, the CoPt films were annealed at 700 degree sign C for 120 min to produce the magnetically hard, fully ordered L1{sub 0} phase. The presence of exchange coupling in the bilayers was verified by magnetic hysteresis and recoil measurements and showed that only for Co thicknesses below 6.3 nm was this layer (in its as-deposited state) coupled through its full thickness to the CoPt layer. Annealing the bilayer samples at 300 and 550 degree sign C for 20 min resulted in improvement of the interlayer magnetic coupling and produced clear differences in the magnetic reversal coherency and the recoil curves. However, for some samples, the improved coupling resulted in a decrease in coercivity, indicating that there is an optimum in the coupling strength for themore » attainment of high coercivity. Transmission electron microscopy studies of the bilayers in plan view showed that the increased interlayer coupling with annealing was a result of improved granular epitaxy of Co to CoPt. (c) 2000 American Institute of Physics.« less

Authors:
 [1];  [2];  [2];  [3];  [3]
  1. Department of Materials Science and Engineering, Lehigh University, Bethlehem, Pennsylvania 18015 (United States)
  2. Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
  3. Materials and Chemical Sciences Division, Department of Applied Sciences, Brookhaven National Laboratory, Upton, New York 11973 (United States)
Publication Date:
OSTI Identifier:
20216265
Resource Type:
Journal Article
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 87; Journal Issue: 9; Other Information: PBD: 1 May 2000; Journal ID: ISSN 0021-8979
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COBALT ALLOYS; PLATINUM ALLOYS; EXCHANGE INTERACTIONS; ANNEALING; THIN FILMS; MICROSTRUCTURE; PERMANENT MAGNETS; SPUTTERING; COERCIVE FORCE; TRANSMISSION ELECTRON MICROSCOPY; EXPERIMENTAL DATA

Citation Formats

Kim, J., Barmak, K., De Graef, M., Lewis, L. H., and Crew, D. C. Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films. United States: N. p., 2000. Web. doi:10.1063/1.372635.
Kim, J., Barmak, K., De Graef, M., Lewis, L. H., & Crew, D. C. Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films. United States. doi:10.1063/1.372635.
Kim, J., Barmak, K., De Graef, M., Lewis, L. H., and Crew, D. C. Mon . "Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films". United States. doi:10.1063/1.372635.
@article{osti_20216265,
title = {Effect of annealing on magnetic exchange coupling in CoPt/Co bilayer thin films},
author = {Kim, J. and Barmak, K. and De Graef, M. and Lewis, L. H. and Crew, D. C.},
abstractNote = {Thin film CoPt/Co bilayers have been prepared as a model system to investigate the relationship between microstructure and exchange coupling in two-phase nanocomposite permanent magnets. The bilayers were prepared by magnetron sputter deposition of near-equiatomic CoPt with a thickness of 25 nm onto oxidized Si wafers. In the as-deposited state, CoPt had the A1 (fcc) structure and was magnetically soft. Before reinsertion into the sputtering chamber for the deposition of 2.8-16.7 nm thick Co layers, the CoPt films were annealed at 700 degree sign C for 120 min to produce the magnetically hard, fully ordered L1{sub 0} phase. The presence of exchange coupling in the bilayers was verified by magnetic hysteresis and recoil measurements and showed that only for Co thicknesses below 6.3 nm was this layer (in its as-deposited state) coupled through its full thickness to the CoPt layer. Annealing the bilayer samples at 300 and 550 degree sign C for 20 min resulted in improvement of the interlayer magnetic coupling and produced clear differences in the magnetic reversal coherency and the recoil curves. However, for some samples, the improved coupling resulted in a decrease in coercivity, indicating that there is an optimum in the coupling strength for the attainment of high coercivity. Transmission electron microscopy studies of the bilayers in plan view showed that the increased interlayer coupling with annealing was a result of improved granular epitaxy of Co to CoPt. (c) 2000 American Institute of Physics.},
doi = {10.1063/1.372635},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 9,
volume = 87,
place = {United States},
year = {2000},
month = {5}
}