NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Induced Anisotropy in FeCo-Based Nanocrystalline Ferromagnetic Alloys (HITPERM) by Very High Field AnnealingVery high magnetic field annealing is shown to affect the magnetic anisotropy in FeCo-base nanocrystalline soft ferromagnetic alloys. Alloys of composition Fe(44.5)Co(44.5)Zr(7)B(4) were prepared by melt spinning into amorphous ribbons, then wound to form toroidal bobbin cores. One set of cores was crystallized in a zero field at 600 deg. C for 1 h, then, field annealed at 17 tesla (T) at 480 deg. C for 1 h. Another set was crystallized in a 17-T field at 480 deg. C for 1 h. Field orientation was transverse to the magnetic path of the toroidal cores. An induced anisotropy is indicated by a sheared hysteresis loop. Sensitive torque magnetometry measurements with a Si cantilever sensor indicated a strong, uniaxial, longitudinal easy axis in the zero-field-crystallized sample. The source is most likely magnetoelastic anisotropy, caused by the residual stress from nanocrystallization and the nonzero magnetostriction coefficient for this material. The magnetostrictive coefficient lambda(5) is measured to be 36 ppm by a strain gage technique. Field annealing reduces the magnitude of the induced anisotropy. Core loss measurements were made in the zero-field-crystallized, zero-field-crystallized- than-field-annealed, and field-crystallized states. Core loss is reduced 30%-50% (depending on frequency) by field annealing. X-ray diffraction reveals no evidence of crystalline texture or orientation that would cause the induced anisotropy. Diffusional pair ordering is thought to be the cause of the induced anisotropy. However, reannealing the samples in the absence of a magnetic field at 480 deg. C does not completely remove the induced anisotropy.
Document ID
20100017268
Acquisition Source
Glenn Research Center
Document Type
Reprint (Version printed in journal)
Authors
Johnson, F.
(National Inst. of Standards and Technology Gaithersburg, MD, United States)
Garmestani, H.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Chu, S.-Y.
(Carnegie-Mellon Univ. Pittsburgh, PA, United States)
McHenry, M. E.
(Carnegie-Mellon Univ. Pittsburgh, PA, United States)
Laughlin, D. E.
(Carnegie-Mellon Univ. Pittsburgh, PA, United States)
Date Acquired
August 24, 2013
Publication Date
July 1, 2004
Publication Information
Publication: IEEE Transactions on Magnetics
Publisher: IEEE Magnetics Society
Volume: 40
Issue: 4
ISSN: 0018-9464
Subject Category
Metals And Metallic Materials
Report/Patent Number
AD-A515260
Funding Number(s)
CONTRACT_GRANT: NGT3-52379
Distribution Limits
Public
Copyright
Other
Keywords
FERROMAGNETIC ALLOYS

Available Downloads

There are no available downloads for this record.
No Preview Available