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Displaying 51 - 75 of 240

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

Direct Imaging of Current Driven Domain Walls in Ferromagnetic Nanostripes

May 21, 2009
Author(s)
Willard C. Uhlig, Michael J. Donahue, Daniel T. Pierce, John Unguris
To better understand the response of domain walls to current induced spin transfer torques, we have directly imaged the internal magnetic structure of domain walls in current-carrying ferromagnetic nanostripes. Domain wall images were acquired both while a

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

Manipulation of the Vortex Motion in Nanostructured Ferromagnetic/Superconductor Hybrids

April 30, 2007
Author(s)
A V. Silhanek, W Gillijns, V V. Moshchalkov, V Metlushko, F Gozzini, B Ilic, Willard C. Uhlig, John Unguris
The authors investigate the rectified motion of vortices in superconducting films deposited on top of a close-packed array of open in-plane magnetized triangular micromagnets. The dc voltage induced by the vortex drift under an ac excitation is recorded

SEMPA Imaging for Spintronics Applications

January 1, 2007
Author(s)
John Unguris, Daniel T. Pierce, Seok-Hwan Chung
Scanning Electron Microscopy with Polarization Analysis (SEMPA) provides high resolution (10 nm) magnetization images simultaneously with, but independent of, the topography. Such information is very useful in studying spintronics devices as illustrated by

Magnetic Properties of Co/GaAs(110)

December 4, 2006
Author(s)
T Monchesky, John Unguris
We observed three magnetic states of an ultrathin, atomically well-ordered Co film grown on a cleaved GaAs(110) substrate. For a Co thickness less than 3.4 monolayers (ML), we find a ferromagnetically dead layer associated with the formation of interfacial

Anisotropy of Magnetization Reversal and Magnetoresistance in Square Arrays of Permalloy Nano-Rings

October 1, 2006
Author(s)
A Goncharov, A Zhukov, V Metlushko, G Bordignon, H Fangohr, C de Groot, John Unguris, Willard C. Uhlig, G Karapetrov, B Ilic, P A. de Groot
Magnetization reversal mechanisms and the impact of magnetization direction are studied in square arrays of interconnected circular permalloy nanorings using magnetooptical Kerr effect, local imaging, numerical simulations, and transport techniques

The Effect of Stress Induced Anisotropy in Patterned FeCo Thin Film Structures

April 24, 2006
Author(s)
W Yu, J A. Bain, Willard C. Uhlig, John Unguris
In this work, 1 υm thick FeCeo films with -320 MPa compressive stress and FeCo/NiFe films with 600 MPa tensile stress were patterened into 5υm x 20 υm elements. The stress anisotropy resulting from patterning was measured using x-ray diffraction to be 220

The Effect of Stress Induced Anisotropy in Patterned FeCo Thin Film Structures

April 1, 2006
Author(s)
Wonpil Yu, J A. Bain, Willard C. Uhlig, John Unguris
The usage of high moment FeCo alloys in magnetic recording heads can result in stress induced anisotropy due to the high magnetostriction constants of FeCo alloys with 30% to 50% Co. In this work, 1um thick FeCo (65% Fe, 35% Co) sheet films with a Cu

Current Induced DomainWall Distortions

January 1, 2006
Author(s)
Willard C. Uhlig, John Unguris
We have directly imaged the spin transfer torque induced distortion of domain walls in current carrying ferromagnetic wires. Domain walls ranging from vortex walls in wide (1 m) wires, to transverse walls in narrow (100 nm) wires were studied. Scanning

New Magnetic Phases of bcc-Co Thin Films

January 1, 2005
Author(s)
T Monchesky, John Unguris
We have been able to observe two new magnetic phases of ultrathin Co by growing atomically well ordered Co films on cleaved GaAs(110) substrates. For a Co thickness less than 3.4 monolayers (ML), we find a ferromagnetically dead layer associated with the