Magnetic Annealing in Perminvar. I. Structural Origin

Heidenreich, R. D.; Nesbitt, E. A.; Burbank, R. D.

doi:10.1063/1.1777004

Cited by 53 publications

(12 citation statements)

References 6 publications

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“…It is believed to be related to the fact that they suppress long-range ordering and so may favour local ordering in the field direction. This new mechanism, which we have found to operate in cobaltrich amorphous oxides, appears to be similar to that identified by Heidenreich et al (1959) to be responsible for field annealing in crystalline Co-Ni-Fe (Permendur and Permalloy) alloys and field-induced ordering in Ni3Fe by Nesbitt et al (1965).…”

Section: Relationship Between N~icrostructure and Field-induced Anisosupporting

confidence: 85%

New mechanism for field‐induced anisotropy of cobalt‐rich amorphous alloys

Kim

O’Handley

1995

Journal of Microscopy

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SUMMARY It is generally assumed that amorphous magnetic alloys respond to field annealing by a process of local directional ordering which leaves the amorphous structure intact. We have made a comparative microstructural study of field‐annealed Co95‐xFe5(BSi)x amorphous alloys using transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) with thin sections parallel to the ribbon surface. Field annealing response was measured from anisotropy in low‐field hysteresis loops. These alloys show appreciable surface crystallization for annealing as much as 80 K below the bulk crystallization temperature. The surface crystallization proceeds by a known mechanism (selective oxidation) to which we have added a more detailed understanding. Three steps are involved: (1) formation of an amorphous borosilicate surface oxide layer during annealing; (2) depletion of glass stabilizing elements (boron and silicon) from the underlying amorphous metal substrate; (3) primary crystallization of the destabilized, metal‐enriched subsurface layer to an fee or hep cobalt‐rich phase. Striking differences in the microstructural morphology were revealed for different glass former ratios B/Si. For high B/Si ratios, the surface crystallites are predominantly fee Co and show a high density of oxygen faults. For low B/Si ratios, the surface crystallites are predominantly hep Co and almost free of faults. Response to field annealing is proportional to the B/Si ratio and correlates with the presence of oxygen faults in surface crystallites. Electron diffraction and microprobe analysis indicate that the surface oxide in silicon‐rich alloys is a dense silica glass which appears to be an effective diffusion barrier to oxygen. The surface oxide in boron‐rich alloys is a more porous oxide richer in B2O3. These observations appear to be related to those from perminvar alloys where oxygen was found to be necessary for field annealing to be effective.

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Section: Relationship Between N~icrostructure and Field-induced Anisosupporting

confidence: 85%

New mechanism for field‐induced anisotropy of cobalt‐rich amorphous alloys

Kim

O’Handley

1995

Journal of Microscopy

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“…From the hysteresis loop of barium ferrite and polyaniline nanocomposites, it has been observed that the material possesses high retentivity (Mr) and coercive force (Hc). The observed hysteresis loop shows little variation from the regular magnetization curve of barium ferrite which may be attributed to annealing conditions and also to the increase in the iron concentration [124]. This type of behavior is observed in ferrites having high Curie temperature and to the slow cooling of the sample which causes slight oxidation of the sample.…”

Section: Magnetic Studiesmentioning

confidence: 74%

Designing of Nano Composites of Conducting Polymers for EMI Shielding

Dhawan¹,

Ohlan²,

Singh³

2011

Advances in Nanocomposites - Synthesis, Characterization and Industrial Applications

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“…1 Results for P e r m a l l o y a r e of the g r e a t e s t interest, p a r t i c u l a r l y since o x i d e s a r e t h o u g h t to p l a y a role in the origin of anisotropy in magnetic films (8). 1 Results for P e r m a l l o y a r e of the g r e a t e s t interest, p a r t i c u l a r l y since o x i d e s a r e t h o u g h t to p l a y a role in the origin of anisotropy in magnetic films (8).…”

Section: Discussionmentioning

confidence: 99%

Effect of Aging on Surface Roughness of Thin Films

Prosen¹,

Kivel²,

Gran³

et al. 1964

J. Electrochem. Soc.

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locations had propagated from several lines of damage into the surrounding regions during annealing, and the driving force for these dislocations was considered to be the associated stresses.However, although strains are present beneath the "visible" damage, i.e., the chips, cracks, and dislocations, little appears to be known about their nature or extent. The strains are elastic and arise from the stresses imposed by the "visible" damage, and also perhaps from the presence of point defects, e.g., vacancies. Such point defects could be present without being detected by the transmission electron microscope method.When such specimens are chemically polished with CP4, the transmission electron micrographs show that the attack commences preferentially at the lines of damage. After 1 sec, the damage is partly removed and grooves begin to form along the lines of damage. After 3 sec, no damage can be detected and the grooves are appreciably wider. Thereafter, the grooves continue to increase in width, but not apparently to change much in depth. The latter may also be deduced from the interference micrographs of Fig. 1. The sequence is illustrated diagrammatically in Fig. 6. The reason for the preferential attack is undoubtedly due to the strains associated with the lines of damage.The question still remains as to why the scratch-

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Magnetic Annealing in Perminvar. I. Structural Origin

Cited by 53 publications

References 6 publications

New mechanism for field‐induced anisotropy of cobalt‐rich amorphous alloys

New mechanism for field‐induced anisotropy of cobalt‐rich amorphous alloys

Designing of Nano Composites of Conducting Polymers for EMI Shielding

Effect of Aging on Surface Roughness of Thin Films

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