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15 May 2005

Volume 97, Issue 10, Articles (10xxxx)

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back to top Instrumentation and Measurement Techniques

Dynamic following of off-centered hard disk tracks in spin-stand imaging

C. Tseng, I. Mayergoyz, C. Tse, P. McAvoy, and C. Krafft

J. Appl. Phys. 97, 10R301 (2005); http://dx.doi.org/10.1063/1.1846231 (3 pages) | Cited 2 times

Online Publication Date: 17 May 2005

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A dynamic track-following technique has been developed that enables real-time reading of on-track data from off-centered hard disks on a spin stand. The technique makes use of piezoelectric transducers (PZT’s) to dynamically control the radial displacement of the read head to follow off-centered tracks. Controlling algorithms based on the Preisach model of hysteresis have been devised to compensate for the hysteretic effects of the PZT. Techniques for extracting the trajectories of off-centered hard disk tracks and special methods of selecting the initial phase of these tracks and locking the phase thereafter have also been developed. The track-following technique has been demonstrated to dynamically follow off-centered commercial hard disks with a track density of 90 kilotrack per inch mounted on a spin stand.
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85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.40.Gb Dynamic properties (dynamic susceptibility, spin waves, spin diffusion, dynamic scaling, etc.)

Magneto-optic studies of garnets subject to rotating magnetic fields

Iulian Nistor, I. D. Mayergoyz, and C. Krafft

J. Appl. Phys. 97, 10R302 (2005); http://dx.doi.org/10.1063/1.1846292 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2005

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This paper presents the study of the magneto-optical effects in garnets with in-plane magnetization under rotating magnetic fields. The samples are garnets of composition (LuBi)3(FeGa)5O12 epitaxially grown on (100) substrates. It is shown that the optical response of the samples can be used to precisely determine the orientation of the crystallographic axes. In addition, an optical method is presented to quantitatively measure the cubic crystalline anisotropy field.
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75.50.Gg Ferrimagnetics
78.20.Ls Magneto-optical effects
68.55.-a Thin film structure and morphology
81.05.Je Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
78.66.Nk Insulators
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
68.55.A- Nucleation and growth

Dielectric resonance in magnetic resonance imaging: Signal inhomogeneities in samples of high permittivity

Masaki Sekino, Hiroaki Mihara, Norio Iriguchi, and Shoogo Ueno

J. Appl. Phys. 97, 10R303 (2005); http://dx.doi.org/10.1063/1.1847211 (3 pages) | Cited 4 times

Online Publication Date: 17 May 2005

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A distinctive signal inhomogeneity arises in magnetic resonance (MR) images of samples whose dimension is comparable to the wavelength of electromagnetic fields at the resonant frequency. In this study, spatial distributions of magnitude and phase of MR signals in cylindrical phantoms were obtained by theoretical calculations and experiments. As the diameter of the phantom approaches the wavelength of electromagnetic fields in the phantom, the center of the phantom exhibited high magnitude of MR signals. An increase in conductivity resulted in a suppression of the signal inhomogeneity due to skin effect. In addition, the increase in conductivity caused a phase delay at the center of the phantom.
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87.61.-c Magnetic resonance imaging
77.65.Fs Electromechanical resonance; quartz resonators
87.85.J- Biomaterials

Use of microscale coplanar striplines with indium tin oxide windows in optical ferromagnetic resonance measurements

P. S. Keatley, V. V. Kruglyak, A. Barman, S. Ladak, R. J. Hicken, J. Scott, and M. Rahman

J. Appl. Phys. 97, 10R304 (2005); http://dx.doi.org/10.1063/1.1849071 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2005

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It is shown that a coplanar stripline structure containing indium tin oxide windows can be used to perform optical ferromagnetic resonance measurements on a sample grown on an opaque substrate, using a pulsed magnetic field of any desired orientation. The technique is demonstrated by applying it to a thin film of permalloy grown on a Si substrate. The measured precession frequency was found to be in good agreement with macrospin simulations. The phase of the oscillatory Kerr response was observed to vary as the probe spot was scanned across the coplanar stripline structure, confirming that the orientation of the pulsed field varied from parallel to perpendicular relative to the plane of the sample.
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75.50.Bb Fe and its alloys
84.40.Az Waveguides, transmission lines, striplines
75.70.Ak Magnetic properties of monolayers and thin films
76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
78.20.Ls Magneto-optical effects

Imaging of the dielectric resonance effect in high field magnetic resonance imaging

Hiroaki Mihara, Norio Iriguchi, and Shoogo Ueno

J. Appl. Phys. 97, 10R305 (2005); http://dx.doi.org/10.1063/1.1854291 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2005

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At a high field magnetic resonance imaging (MRI), the interactions between the RF pulse and the high permittivity samples, which cause the B1 field inhomogeneity, can no longer be negligible. We present a postprocessing method of compensating the B1 field inhomogeneity mainly caused by the dielectric resonance. The intensity of the transmitted B1 field is calculated using two spin echo images of the water phantom obtained with different flip angles 45° and 90°. Applying the proposed method, the dielectric resonance of the water in high field MRI is visualized as a quantitative map of the B1 field. The corrected image compensating the B1 field inhomogeneity was also calculated.
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87.61.-c Magnetic resonance imaging
76.60.Lz Spin echoes
77.22.Ch Permittivity (dielectric function)
77.22.Gm Dielectric loss and relaxation

Vector characterization of soft magnetic materials

Z. W. Lin, H. W. Lu, J. G. Zhu, J. J. Zhong, X. L. Wang, and S. Y. Ding

J. Appl. Phys. 97, 10R306 (2005); http://dx.doi.org/10.1063/1.1855571 (3 pages) | Cited 1 time

Online Publication Date: 17 May 2005

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A three-dimensional (3D) magnetic property testing system has been completed and successfully used to measure 3D hysteresis loci of soft magnetic material. This paper presents the techniques to characterize soft magnetic materials under 3D magnetic excitations in detail. Using three couples of excitation coils controlled by a computer to generate the magnetic fields in three orthogonal axes, various types of flux density loci, such as circular or elliptical rotating vectors of flux density with any given orientations in 3D space, can be obtained. Based on 3D finite element analysis and a comparative study, a sandwich arrangement comprising a sample, guard pieces, and search coils with double-layer structure was proposed. Compared with the conventional surface search coils, this arrangement can significantly improve the accuracy of measurement. The comprehensive calibration process and the experimental results of the 3D hysteresis loci of soft magnetic composite materials are also presented.
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75.40.Mg Numerical simulation studies
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Monitoring the fatigue state of steel by evaluating the quasistatic and dynamic magnetic behavior

Lode Vandenbossche, Luc Dupré, and Jan Melkebeek

J. Appl. Phys. 97, 10R307 (2005); http://dx.doi.org/10.1063/1.1855708 (3 pages) | Cited 3 times

Online Publication Date: 17 May 2005

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For the evaluation of fatigue damage progression the application of quasistatic and dynamic magnetic measurements combined with the Preisach hysteresis model and the statistical loss theory is investigated. Throughout the fatigue lifetime hysteresis and excess magnetic behavior, both known to be sensitive to microstructural variations, are monitored. The magnetic evaluation results for fatigue tests executed on two steels depend on their initial microstructure and chemical composition. In addition the effect of low stress amplitude cyclic loading on the magnetic properties of electrical steel is investigated: after 1000 cycles the excess losses are slightly decreased, while hysteresis properties stay invariant.
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75.50.Bb Fe and its alloys
81.05.Bx Metals, semimetals, and alloys
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.70.Bt Mechanical testing, impact tests, static and dynamic loads
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
62.20.M- Structural failure of materials

Surface tension measurement techniques of magnetic fluids at an interface between different fluids using perpendicular field instability

M. Shahrooz Amin, Shihab Elborai, Se-Hee Lee, Xiaowei He, and Markus Zahn

J. Appl. Phys. 97, 10R308 (2005); http://dx.doi.org/10.1063/1.1861374 (3 pages) | Cited 2 times

Online Publication Date: 17 May 2005

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Two measurement techniques to determine the surface tension of ferrofluids using the perpendicular field instability are described. Four ferrofluid layers were examined with magnetic field applied perpendicularly to the surface of (1) oil-based ferrofluid in air; (2) water-based ferrofluid in air, (3) oil-based ferrofluid, and (4) fluorocarbon-based ferrofluid, both below a blend of 50% n-Propyl alcohol and 50% deionized water (propanol). Surface tension was accurately calculated by utilizing the measured Taylor wavelength from measurements of incipient fluid instability peaks and the measured densities of fluids. For cases (1) and (2), the calculated surface tension values were in good agreement with a tensiometer measurement. No accurate tensiometer measurements were conducted for the superposed liquids (3) and (4) since accurate tensiometer measurements are difficult for a two fluid layer system. The second less accurate method used the ferrofluid’s nonlinear Langevin magnetization characteristics to compute the surface tension from incipience of interfacial instability conditions. Discrepancies between the surface tensions measured by the two methods were probably due to the ferrofluid particle size distributions and the strong dependence of the ferrofluid magnetization on particle size.
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75.50.Mm Magnetic liquids
75.50.Tt Fine-particle systems; nanocrystalline materials
68.03.Cd Surface tension and related phenomena
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
47.20.Dr Surface-tension-driven instability
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