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Search Publications by: Robert D. McMichael (Assoc)

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Displaying 76 - 100 of 314

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