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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Magnetic microstructure of Fe84Nb7B9 alloys observed by electron holography

Youhui Gao, Daisuke Shindo, Teruo Bitoh, and Akihiro Makino

J. Appl. Phys. 93, 7462 (2003); http://dx.doi.org/10.1063/1.1537695 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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The microstructure, magnetic properties and magnetic structure of crystallized Fe84Nb7B9 samples are studied in this article. It is found that the size of the body-centered-cubic Fe crystallites is independent of the annealing temperature. The volume fraction of the amorphous phase decreases with an increase in annealing temperature and iron boride precipitates form at temperatures over 973 K. Excellent soft magnetic properties are obtained in the sample annealed at 923 K which has large uniform domains with smooth and straight walls, whereas precipitates of Fe boride in the sample annealed at 973 K degrade the magnetic softness. Their magnetization processes are pure magnetization rotation dominated by uniaxial anisotropy. The thick amorphous phase matrix and strong internal stray field in the sample annealed at 773 K lead to a magnetic ripple structure. The domain wall movement is strongly pinned by anisotropy fluctuations. The longitudinal wavelength of the magnetic ripples increases with a decrease in temperature, and disappears at temperatures below 230 K. © 2003 American Institute of Physics.
Show PACS
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
81.05.Bx Metals, semimetals, and alloys
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.30.Bx Phase diagrams of metals, alloys, and oxides
61.05.jp Electron holography
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
75.60.Ch Domain walls and domain structure
75.30.Et Exchange and superexchange interactions
75.30.Gw Magnetic anisotropy
64.75.-g Phase equilibria
81.30.Mh Solid-phase precipitation

Investigation of magnetic and magnetomechanical hysteresis properties of Fe–Si alloys with classical and mechanical Barkhausen effects and magnetoacoustic emission

B. Augustyniak, L. Piotrowski, M. Radczuk, M. Chmielewski, and H. Hauser

J. Appl. Phys. 93, 7465 (2003); http://dx.doi.org/10.1063/1.1558661 (3 pages)

Online Publication Date: 9 May 2003

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Grain oriented Fe 3.5% Si sheet samples with a Goss (GO) microstructure and Fe 3.5% samples with nonoriented (NO) grains were tested using two Barkhausen effects, the classical Barkhausen effect (HBE) and the mechanical Barkhausen effect (MBE), as well as the magnetoacoustic emission (MAE). The aim of the work was to present further evidence that the B(H) hysteresis with effects like HBE and MAE, and magnetomechanical hysteresis with MBE are correlated via internal stress barriers pinning domain walls (DWs). In the case of a GO alloy, the long axis of the sample was parallel to the [100], [110], and [111] directions with respect to the rolling direction. The HBE and MAE were measured using a C-core electromagnet supplied with a triangular wave form of current intensity. The MBE intensity was recorded during a monotonous increase of shear stress using a torque machine. The maxima of MBE intensity for the “first load” mode for a NO sample and for three GO samples indicate an internal stress distribution pinning 90° DWs. The MAE plots reveal at least two maxima which are well correlated with H strength values where creation and annihilation of magnetic domains appears. Since the MBE and MAE are associated with abrupt jumps of 90° DW, the existence of MBE and MAE reinforces the fact that such DWs are present in the tested samples. These walls belong mainly to the secondary closure domains at GO alloys and to closure domains at NO alloy. © 2003 American Institute of Physics.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Bb Fe and its alloys
75.80.+q Magnetomechanical effects, magnetostriction
75.60.Ch Domain walls and domain structure

Magnetic properties of Fe thin films on Ag submicrometer islands

C. C. Yu, W. C. Cheng, W. B. Lee, S. Y. Chen, Y. Liou, and Y. D. Yao

J. Appl. Phys. 93, 7468 (2003); http://dx.doi.org/10.1063/1.1537696 (3 pages) | Cited 7 times

Online Publication Date: 9 May 2003

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Face-centered-cubic Ag(100) submicrometer islands on an RCA-cleaned Si(100) substrate were fabricated by molecular beam epitaxy; a 500 Å Fe thin film was then grown onto Ag films at 100 °C. We experimentally demonstrate that the magnetic behavior of Fe films is strongly dependent on the thickness and morphology of the Ag underlayer. The Ag film, in order to reduce the surface free energy, forms isolated three-dimensional square islands with {111} sidewall on the Si(100) substrate. The average height, grain size and surface roughness of these Ag islands were tuned by varying the deposition thickness of the Ag film. The in-plane easy axis of the Fe film was rotated 45° while the thickness of the Ag underlayer reaches 100 Å and the Ag rough surface provides a source of domain wall pinning. © 2003 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.35.Md Surface thermodynamics, surface energies
75.70.Kw Domain structure (including magnetic bubbles and vortices)
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