Off-axis electron holography of ferromagnetic multilayer nanowires
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A1S6 (Canada)
- Apollo Microwaves, 1650 Trans-Canada Highway, Dorval, Quebec H9P 1H7 (Canada)
- Department of Engineering Physics, École Polytechnique de Montréal, Montréal, Quebec, H3C 3A7 Canada (Canada)
- Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark)
- Department of Mechanical Engineering, University of Victoria, Victoria, British Columbia V8W 3P6 (Canada)
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Institute for Microstructure Research, D-52425 Jülich (Germany)
- Department of Physics, Arizona State University, Tempe, Arizona 85287-1504 (United States)
We have used electron holography to investigate the local magnetic behavior of isolated ferromagnetic nanowires (NWs) in their remanent states. The NWs consisted of periodic magnetic layers of soft, high-saturation magnetization CoFeB alloys, and non-magnetic layers of Cu. All NWs were fabricated by pulsed-potential electrodeposition in nanoporous alumina membranes. The NW composition and layer thicknesses were measured using scanning transmission electron microscopy and energy dispersive spectroscopy. The magnetization of individual NWs depended upon the thicknesses of the layers and the direction of an external magnetic field, which had been applied in situ. When the CoFeB was thicker than the diameter (50 nm), magnetization was axial for all external field directions, while thinner layers could be randomized via a perpendicular field. In some cases, magnetization inside the wire was detected at an angle with respect to the axis of the wires. In thinner Cu/CoFeB (<10 nm each) multilayer, magnetic field vortices were detected, associated with opposing magnetization in neighbouring layers. The measured crystallinity, compositions, and layer thicknesses of individual NWs were found to be significantly different from those predicted from calibration growths based on uniform composition NWs. In particular, a significant fraction of Cu (up to 50 at. %) was present in the CoFeB layers such that the measured magnetic induction was lower than expected. These results will be used to better understand previously measured effective anisotropy fields of similar NW arrays.
- OSTI ID:
- 22308968
- Journal Information:
- Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 2 Vol. 116; ISSN JAPIAU; ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANISOTROPY
BORON COMPOUNDS
COBALT COMPOUNDS
COPPER
ELECTRODEPOSITION
FERROMAGNETIC MATERIALS
HOLOGRAPHY
IRON COMPOUNDS
LAYERS
MAGNETIC FIELDS
MAGNETIZATION
MEMBRANES
NANOWIRES
PERIODICITY
QUANTUM WIRES
SATURATION
SPECTROSCOPY
TERNARY ALLOY SYSTEMS
THICKNESS
TRANSMISSION ELECTRON MICROSCOPY