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Electromagnetics and Photonics

Materials Science and Engineering Publications

Ames Laboratory

Articles 1 - 6 of 6

Full-Text Articles in Physics

In Situ Applied Field Imaging Of A Magnetic Tunnel Junction Using Magnetic Force Microscopy, J. S. Leib, Chester C.H. Lo, John E. Snyder, David C. Jiles May 2003

In Situ Applied Field Imaging Of A Magnetic Tunnel Junction Using Magnetic Force Microscopy, J. S. Leib, Chester C.H. Lo, John E. Snyder, David C. Jiles

Materials Science and Engineering Publications

Knowledge of domain behavior in magnetic tunnel junctions is an essential component, together with knowledge of the electron band structure, for understanding their magnetoelectronic properties. To this purpose, the magnetization reversal processes of a multilayertunnel junction of structure substrate/NiFe/AlOx/FeCo/CrPtMn/Al of tapered half-ellipsoid shape have been imaged using a magnetic force microscope(MFM) within situ applied magnetic fields. Stripe domains through both the stack and free layers observed at zero applied field were erased by a ∼100 Oe field applied to the left followed by applying a small field to the right. Magnetic domain structure ...


Lorentz Transmission Electron Microscopy And Magnetic Force Microscopy Characterization Of Nife/Al-Oxide/Co Films, Andrew C. C. Yu, Chester C.H. Lo, Amanda K. Petford-Long, David C. Jiles, Terunobu Miyazaki Jan 2002

Lorentz Transmission Electron Microscopy And Magnetic Force Microscopy Characterization Of Nife/Al-Oxide/Co Films, Andrew C. C. Yu, Chester C.H. Lo, Amanda K. Petford-Long, David C. Jiles, Terunobu Miyazaki

Materials Science and Engineering Publications

Magnetization reversal process of NiFe/Al-oxide/Co junction films was observed directly using Lorentztransmission electron microscopy (LTEM) and magnetic force microscopy(MFM).In situmagnetizing experiments performed in both LTEM and MFM were facilitated by a pair of electromagnets, which were mounted on the sample stages. A two-stage magnetization reversal process for the junction film was clearly observed in LTEM with NiFe magnetization reversed first via domain wall motion followed by Co magnetization reversal via moment rotation and domain wall motion. Reversal mechanism and domain characteristics of the NiFe and Co layers showed very distinctive features. The magnetization curve of ...


Magnetic Force Microscopy Study Of Magnetization Reversal In Sputtered Fesial(N) Films, Chester C.H. Lo, J. E. Snyder, J. S. Leib, R. Chen, B. Kriegermeier-Sutton, Matthew J. Kramer, David C. Jiles, M. T. Kief Mar 2001

Magnetic Force Microscopy Study Of Magnetization Reversal In Sputtered Fesial(N) Films, Chester C.H. Lo, J. E. Snyder, J. S. Leib, R. Chen, B. Kriegermeier-Sutton, Matthew J. Kramer, David C. Jiles, M. T. Kief

Materials Science and Engineering Publications

The magnetization reversal in a series of rf-sputtered FeSiAl(N) films has been studied using magnetic force microscopy. A system has been developed which has the capability to image domain structure while an in-plane magnetic field is applied in situ. All films exhibited a stripe domain structure in zero applied field which was indicative of a perpendicular component of domain magnetization which alternates in sign. All films showed a similar sequence of magnetization processes: on reducing the applied field from saturation a fine stripe domain structure nucleated and then coarsened as the field was decreased to zero. Local switching of ...


Temperature Dependence Of The Magnetomechanical Effect In Metal-Bonded Cobalt Ferrite Composites Under Torsional Strain, Y. Chen, John E. Snyder, Kevin W. Dennis, R. William Mccallum, David C. Jiles May 2000

Temperature Dependence Of The Magnetomechanical Effect In Metal-Bonded Cobalt Ferrite Composites Under Torsional Strain, Y. Chen, John E. Snyder, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Materials Science and Engineering Publications

Metal-bonded cobaltferrite composites are promising candidates for torquesensors and other magnetostrictive sensing and actuating applications. In the present study, the temperature dependence of the magnetomechanical effect in a ring-shape cobaltferrite composite under torsional strain has been investigated in the temperature range of −37 to 90 °C. The changes of external axial magnetic field were measured as a function of applied torque. Magnetomechanical sensitivity of ΔHext/Δτ=65 A N−1 m−2 was observed with a magnetomechanical hysteresis of Δτ=±0.62 N m at room temperature (22 °C). These were then measured as a function of temperature. Both decreased ...


Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams May 1993

Modeling Of Micromagnetic Barkhausen Activity Using A Stochastic Process Extension To The Theory Of Hysteresis, David C. Jiles, Levent B. Sipahi, G. Williams

Materials Science and Engineering Publications

Recent work by Bertotti [IEEE Trans. Magn. MAG‐24, 621 (1988)] and others has shown that it is possible to model the micromagnetic Barkhausen discontinuities at the coercive point using a two‐parameter stochastic model. However, the present formulation of the model is restricted to limited regions of the hysteresis curve over which dM/dH is approximately constant and whendH/dt is held at a constant rate. A natural extension of this model is to take the basic result, in which the level of Barkhausen activity in one time period is related to the activity in the previous time ...


Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler May 1993

Comprehensive Analysis Of Barkhausen Emission Spectra Using Pulse Height Analysis, Frequency Spectrum, And Pulse Wave Form Analysis, Levent B. Sipahi, David C. Jiles, D. Chandler

Materials Science and Engineering Publications

The dependence of magnetic Barkhausen emissions (MBE) upon both field excitation and detection frequencies and excitation wave form was studied in order to investigate two of several crucial factors which affect the emissions. Sinusoidal, triangular, and square wave forms were used to generate the MBE and the pulse height spectra, frequency spectra, and pulse wave forms of these signals were analyzed. The frequency spectra of sinusoidal and triangular alternating field excitations showed similar behavior but the spectrum under square wave excitation was different due to the existence of high frequency components during square wave switching. As yet, no common standard ...