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Search Publications by: Robert D. McMichael (Fed)

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Displaying 51 - 75 of 160

A new connection between electricity and magnetism

February 9, 2009
Author(s)
Robert D. McMichael, Mark D. Stiles
A Viewpoint on ``Universal Electromotive Force Induced by Domain Wall Motion,'' Shengyuan A. Yang, Geoffrey S. D. Beach, Carl Knutson, Di Xiao, Qian Niu, Maxim Tsoi and James L. Erskine.

400-Fold Reduction in Saturation Field by Interlayering

January 13, 2009
Author(s)
William F. Egelhoff Jr., John E. Bonevich, Philip Pong, John Unguris, Robert D. McMichael, Gery R. Stafford, Carlos R. Beauchamp
The buildup of stress with increasing thickness of magnetic thin films is a common phenomenon that often induces undesirable saturation fields that can convert an otherwise magnetically soft film into a magnetically hard one. We have found that by

A New Spin on the Doppler Effect

October 17, 2008
Author(s)
Mark D. Stiles, Robert D. McMichael
The coupling between ferromagnetism and electrical current has recently been the object of intense study because of the combination of interesting scientific developments and the potential technological impact. This coupling is mediated by spin current

A Mean-Field Model of Extrinsic Line Broadening in Ferromagnetic Resonance

October 16, 2008
Author(s)
Robert D. McMichael
A model of ferromagnetic resonance in inhomogeneous films is described that includes interactions in a mean-field approximation. The mean-field model yields linewidth values that span the range from intrinsic linewidth for strong interactions to fully

Shape Effects in Ferromagnetic Resonance of Nanosize Rectangular Permalloy Arrays

October 16, 2008
Author(s)
Martha Pardavi-Horvath, Robert D. McMichael
In-plane and out-of-plane ferromagnetic resonance measurements were performed on arrays of Permalloy rectangles, prepared by interference lithography. In the absence of crystalline anisotropy, the shape anisotropy dominates the angular dependence of the

The Periodic Table of Damping in Doped Ni 80 Fe 20 Thin Films

October 16, 2008
Author(s)
J O. Rantschler, D Pulugurthaand, Andrew P. Chen, L M. Connors, Audie M. Castillo, Alexander J. Shapiro, William F. Egelhoff Jr., Brian B. Maranville, Robert D. McMichael
The effect of doping on the magnetic damping parameter of Ni80Fe20 is measured for 21 transition metal dopants:Ti, V, Cr, Mn, Co, Cu, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au. For most of the dopants, the damping parameter increases

Thickness Dependence of Magnetic Film Edge Properties in Ni 80 Fe 20 Stripes

October 16, 2008
Author(s)
Robert D. McMichael, C A. Ross, V P. Chuang
Measurements of trapped spinwave edge modes in transversely magnetized stripe arrays of Ni80Fe20 largely confirm pervious theoretical predictions for the thickness dependence of the edge saturation field Hsat and the effective out-of-plane edge anisotropy

Preoxidation as a general approach to suppressing orange-peel coupling in magnetic tunnel junctions

October 1, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have found that preoxidation of the bottom electrode prior to deposition of Al 2O 3 or MgO is very effective as a general approach to suppressing orange-peel coupling in magnetic tunnel junctions. When orange-peel coupling is suppressed, the hard-axis

Soft magnetic layers for low-field-detection magnetic sensors

May 18, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Freemon Johnson, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have investigated a wide variety of soft magnetic layers as sense layers for magnetic-field sensors. We find that in thin-film form, some of these soft materials can have susceptibilities (?) approaching those of the corresponding bulk material. In

Characterization of Magnetic Properties at Edges by Edge Mode Dynamics

April 21, 2006
Author(s)
Brian B. Maranville, Robert McMichael, Sudook A. Kim, Ward L. Johnson, C A. Ross, J Cheng
We have used trapped spinwave or edge modes of magnetic precession to probe the magnetic environment near magnetic film edges magnetized perpendicular to the edge. Micromagnetic models of dynamics in stripes reveal that the edge mode frequency-field

Suppression of Orange-Peel Coupling in Magnetic Tunnel Junctions by Preoxidation

April 17, 2006
Author(s)
William F. Egelhoff Jr., Robert McMichael, Cindi L. Dennis, Mark D. Stiles, Alexander J. Shapiro, Brian B. Maranville, Cedric J. Powell
We have found that preoxidation of the bottom Co electrode in magnetic tunnel junctions (MTJs) very effectively suppresses orange-peel coupling. The result is a free layer that is much softer. Work by others has demonstrated that preoxidation is compatible

Performance of Electret Ionization Chambers in Magnetic Field

April 7, 2006
Author(s)
P Kotrappa, L R. Stieff, Timothy F. Mengers, Robert McMichael, Robert D. Shull
Electret Ionization Chambers (EIC) are widely used for measuring radon and radiation. The radiation measured includes alpha, beta and gamma radiation. These detectors do not have any electronics and as such can be introduced into magnetic field regions. It

Magnetic normal modes of nano-elements

May 15, 2005
Author(s)
Robert McMichael, Mark D. Stiles
Micromagnetic calculations are used to determine the eigenfrequencies and precession patterns of some of the lowest-frequency magnetic normal modes of submicron patterned elements. For a Permalloy-like ellipse, 350 nm ¿ 160 nm ¿ 5 nm thick in zero field

Effect of Conformal Roughness on Ferromagnetic Resonance Linewidth in Thin Permalloy Films

May 1, 2005
Author(s)
Brian B. Maranville, J Mallett, Thomas P. Moffat, Robert McMichael, Andrew P. Chen, William F. Egelhoff Jr.
The ferromagnetic resonance line width is a result of both intrinsic damping and contributions from inhomogeneities, which in thin films can be dominated by the roughness. Microstructural measurements and magnetization dynamics are reported here for 50 nm

Magnetic Normal Modes of Nanoelements

May 1, 2005
Author(s)
Robert D. McMichael, Mark D. Stiles
Micromagnetic calculations are used to determine the eigenfrequencies and precession patterns of some of the lowest-frequency magnetic normal modes of submicron patterned elements. For a Permalloy-like ellipse, 350 nm 160 nm 5 nm thick in zero field, the

Origin of Exchange Decoupling Effects in High-Coercivity Air-Annealed CoPd Multilayers

May 1, 2005
Author(s)
William F. Egelhoff Jr., Robert McMichael, J Mallett, Alexander J. Shapiro, Cedric J. Powell, John E. Bonevich, J H. Judy, J H. Thomas, Erik B. Svedberg
We have achieved excellent exchange decoupling of grains in CoPd multilayers by annealing in air at 300 C. Samples exhibit a slope in the hysteresis loop close to 1.0, nucleation fields as large as 1.1 T, and coercivities as large as 1.6 T. These are among

Surface Anisotropy of Permalloy in NM/NiFe/NM Multilayers

May 1, 2005
Author(s)
J O. Rantschler, P J. Chen, Anthony S. Arrott, Robert D. McMichael, William F. Egelhoff Jr., Brian B. Maranville
We have measured surface anisotropy in Permalloy (Py) deposited between two layers of normal metal (NM = Ag, Cu, or Ta) by determining the total perpendicular anisotropy using both the frequency and angular dependence of ferromagnetic resonance

Artifacts That Mimic Ballistic Magnetoresistance

February 1, 2005
Author(s)
William F. Egelhoff Jr., L Gan, H Ettedgui, Y Kadmon, Cedric J. Powell, P J. Chen, Alexander J. Shapiro, Robert McMichael, J Mallett, Thomas P. Moffat, Mark D. Stiles, Erik B. Svedberg
We have investigated the circumstances underlying recent reports of very large values of ballistic magntoresistance (BMR) in nanocontacts between magnetic wires. We find that the geometries used are subject to artifacts due to motion of the wires that