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Search Publications by: Robert D. McMichael (Fed)

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Displaying 26 - 50 of 160

Phase-resolved ferromagnetic resonance using heterodyne detection method

April 28, 2016
Author(s)
Seungha Yoon, Hau Jian Liu, Robert D. McMichael
This paper describes a phase-resolved ferromagnetic resonance (FMR) measurement using a heterodyne method. Spin precession is driven by microwave fields and detected by 1550 nm laser light that is modulated at a frequency slightly shifted with respected to

Noncontact conductivity and dielectric measurement for high throughput roll-to-roll nanomanufacturing

November 23, 2015
Author(s)
Nathan D. Orloff, Christian J. Long, Jan Obrzut, Laurent Millaud, Francesca Mirri, Thomas R. Kole, Robert D. McMichael, Mattei Pasquali, Stephan J. Stranick, James A. Liddle
Advances in roll-to-roll processing of graphene [1] and carbon nanotube [2] have at last led to the continuous production of high-quality coatings and filaments, ushering in a wave of applications for flexible [3], [4] and wearable [5] electronics, woven

Quantitative magnetometry of ferromagnetic nanorods by microfluidic analytical magnetophoresis

September 3, 2015
Author(s)
Andrew L. Balk, Lamar O. Mair, Feng Guo, Carlos M. Hangarter, Pramod Mathai, Robert D. McMichael, Samuel M. Stavis, John Unguris
We introduce an implementation of magnetophoresis to measure the absolute magnetization of ferromagnetic nanorods dispersed in fluids, by analyzing the velocity of single nanorods under an applied magnetic field gradient. A microfluidic guideway prevents

Ferromagnetic resonance measurement using stroboscopic magneto optical Kerr effect

June 7, 2015
Author(s)
Takahiro Moriyama, Seungha Yoon, Robert McMichael
We have developed a novel ferromagnetic resonance measurement technique using the magneto optical Kerr effect. The measurement technique uses microwave-frequency, intensity-modulated light to stroboscopically measure the Kerr angle due to the magnetization

Nonlinear ferromagnetic resonance shift in submicron Permalloy ellipses

February 27, 2015
Author(s)
Feng Guo, Lyubov Belova, Robert D. McMichael
We report a systematic study of nonlinearity in the ferromagnetic resonance of a series of submicron Permalloy ellipses with varying aspect ratios. We focus on the sign of the foldover, a resonance field shift or frequency shift that occurs with high

Magnetic structure and anisotropy of [Co/Pd]_5/NiFe multilayers

January 9, 2015
Author(s)
Larysa Tryputen, Feng Guo, Liu Frank, T. N. Anh Nguyen, Majid Mohseni, Sunjae Chung, Yeyu Fang, Johan Akerman, Robert McMichael, Caroline Ross
The magnetization behavior, magnetic anisotropy and domain congurations of Co/Pd multilayers with perpendicular magnetic anisotropy capped with permalloy is investigated using magnetometry, magnetic force microscopy and ferromagnetic resonance. The

Parametric pumping of precession modes in ferromagnetic nanodisks

March 26, 2014
Author(s)
Feng Guo, Lyubov Belova, Robert McMichael
We report parametric excitation of magnetic precession modes in nanodisks using a parallel pumping configuration. The excitations are detected using a ferromagneitc resonance force microscopy method, and the parallel-pumped spectra reveal nonlinear

Corrosion Detection in Concrete Rebars Using a Spectroscopic Technique

January 11, 2014
Author(s)
Edward J. Garboczi, Paul E. Stutzman, Shuangzhen S. Wang, Nicos Martys, Dat Duthinh, Virgil Provenzano, Shin G. Chou, David F. Plusquellic, Jack T. Surek, Sung Kim, Robert D. McMichael, Mark D. Stiles, Ahmed M. Hassan
Detecting the early corrosion of steel in reinforced concrete is a goal that has been much pursued. Since 2010, NIST has been working on a large project to develop an electromagnetic (EM) probe that detects the actual corrosion products via spectroscopic

Measurement and Simulation of Millimeter Wave Scattering Cross-sections from Steel-Reinforced Concrete

January 11, 2014
Author(s)
Ahmed M. Hassan, Edward Garboczi, Robert McMichael, Jack T. Surek, Mark D. Stiles, David F. Plusquellic, Virgil Provenzano, Paul E. Stutzman, Shuangzhen S. Wang, Sung Kim, Michael D. Janezic, Jason Coder, Nicos Martys, David R. Novotny
Some iron oxide corrosion products exhibit antiferromagnetic magnetic resonances (AFMR) at around 100 GHz at normal temperatures. AFMR can be detected in laboratory conditions, which serves as the basis for a new non-destructive spectroscopic method for

Spin-Wave Propagation in the Presence of Interfacial Dzyaloshinskii-Moriya Interaction

November 4, 2013
Author(s)
Jung-Hwan Moon, Soo-Man Seo, Kyung Jin Lee, Kyoung-Whan Kim, Jisu Ryu, Hyun-Woo Lee, Robert McMichael, Mark D. Stiles
In ferromagnetic thin films, broken inversion symmetry and spin-orbit coupling give rise to interfacial Dzyaloshinskii-Moriya interactions. Analytic expressions for spin-wave properties show that the Dzyaloshinskii-Moriya interaction leads to non

Spectroscopy and imaging of edge modes in Permalloy nanodisks

January 3, 2013
Author(s)
Feng Guo, Lyubov Belova, Robert McMichael
This paper reports spectroscopy and imaging of spin wave modes using ferromagnetic resonance force microscopy (FMRFM) in Permalloy nano-disks with disk diameters that range from 100 nm to 750 nm. The ferromagnetic resonance spectra distinguish multiple

Two dimensional spectroscopic imaging of individual ferromagnetic nanostripes

November 6, 2012
Author(s)
Han-Jong H. Chia, Feng Guo, Lyubov Belova, Robert McMichael
We use ferromagnetic resonance force microscopy (FMRFM) to spectroscopically image the edge modes in individual 700 and 400 nm wide Permalloy stripes with a spatial resolution on the order of 200 nm. The imaging clearly identi es some resonances as edge

Spectroscopic defect imaging in magnetic nanostructure arrays

July 25, 2012
Author(s)
Han-Jong H. Chia, Feng Guo, Lyubov Belova, Robert McMichael
We report a demonstration of spectroscopic defect imaging in an array of ferromagnetic structures using ferromagnetic resonance force microscopy (FMRFM). The arrray of 200 nm diameter circular dots includes a single oval-shaped "defect." The technique

Nanoscale spin wave localization using ferromagnetic resonance force microscopy

February 24, 2012
Author(s)
Han-Jong H. Chia, Feng Guo, Lyubov Belova, Robert D. McMichael
We utilize ferromagnetic resonance force microscopy (FMRFM) to generate and detect multiple localized spin wave modes with spatial dimensions less than 100 nm in ferromagnetic thin films. Localized spin waves are a potentially powerful tool for imaging

Control of magnetic fluctuations by spin current

September 2, 2011
Author(s)
Vladislav E. Demidov, Sergei Urazhdin, Eric Edwards, Mark D. Stiles, Robert McMichael, Sergej O. Demokritov
We utilize micro-focus Brillouin light scattering spectroscopy to study the interaction of spin current generated by the spin Hall effect with magnetic fluctuations in a Permalloy microdisc. We show that the fluctuations can be efficiently enhanced or

Effects of shape distortions and imperfections on mode frequencies and collective linewidths in nanomagnets

March 28, 2011
Author(s)
Hans T. Nembach, Justin M. Shaw, Thomas J. Silva, Ward L. Johnson, Sudook A. Kim, Robert D. McMichael, Pavel Kabos
We used Brillouin light scattering to show that shape distortions in Ni80Fe20 nanoelements can have a dramatic effect on the measured linewidth of certain modes. By intentionally introducing an amount of “egg-like” shape distortion to an ideal elliptical

Effect of interactions on edge property measurements in magnetic multilayers

February 25, 2011
Author(s)
Meng Zhu, Robert D. McMichael
This paper reports effects of inter-film interactions on static and dynamic magnetization behavior at film edges in magnetic trilayer stripe arrays under transverse applied fields. The trilayers consist of two magnetic films of Ni80Fe20, 10 nm and 20 nm

Enhanced magnetization drift velocity and current polarization in (CoFe)_{1-x}Ge_{x} alloys

February 17, 2011
Author(s)
Meng Zhu, Brian D. Soe, Robert D. McMichael, Matthew Carey, Stefan Maat, Jeffrey R. Childress
A spin wave Doppler technique is used to measure the drift velocity of the magnetization in current-carrying (CoFe)_{1-x}Ge_{x} alloys. For a current density of 10^11 A/m2, we obtain a large enhancement of drift velocity from 3.1+/-0.2 m/s for CoFe to 8.2+

Effects of disorder on magnetic vortex gyration

February 15, 2011
Author(s)
Hongki Min, Robert McMichael, Jacques Miltat, Mark D. Stiles
A vortex gyrating in a magnetic disc has two regimes of motion in the presence of disorder. At large amplitudes the vortex core moves quasi-freely through the disorder potential. As the amplitude decreases, the core can become pinned at a particular point

Effects of disorder and internal dynamics on vortex wall propagation

May 26, 2010
Author(s)
Hongki Min, Robert D. McMichael, Michael J. Donahue, Jacques Miltat, Mark D. Stiles
Experimental measurements of domain wall propagation are typically interpreted by comparison to ideal models that ignore the effects of extrinsic disorder and the internal dynamics of domain wall structures. Using micromagnetic simulations we study vortex

Modification of edge mode dynamics of oxidized Ni 80 Fe 20 thin film edges

May 20, 2010
Author(s)
Meng Zhu, Robert D. McMichael
We use ''edge mode'' ferromagnetic resonance (FMR) to probe the magentic properties of oxidized Ni 80Fe 20 (Py) nanostripe edges. The oxidation is carried out using either oxygen plasma or thermal annealing in an oxygen ambient. We find that for both

Phase Diagram of Magnetic Nanodisks measured by SEMPA

January 20, 2010
Author(s)
Seok-Hwan Chung, Robert D. McMichael, Daniel T. Pierce, John Unguris
We use Scanning Electron Microscopy with Polarization Analysis (SEMPA) to image the magnetic domain structures of individual ferromagnetic nanodisks with different diameters and thicknesses, and thereby determine the phase diagram of the magnetic ground