Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by:

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 26 - 50 of 120

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

Zigzag-shaped magnetic sensors

December 13, 2004
Author(s)
Fabio C. da Silva, Willard C. Uhlig, Anthony B. Kos, Susan A. Schima, Joe Aumentado, John Unguris, David P. Pappas
Magnetism in zigzag-shaped thin-film elements is investigated using scanning electron microscopy with polarization analysis, magnetotransport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length

Observation of a geometrically constrained domain wall in epitaxial FCC Co small disks

May 1, 2004
Author(s)
C Vaz, L Lopez-Diaz, M Klaui, J Bland, T Monchesky, John Unguris, Z Cui
The magnetic nanostructure of epitaxial FCC Co/Cu(0 0 1) circular elements (1.7 m in diameter) has been imaged with scanning electron microscopy with polarization analysis. A closed flux configuration (quadrant configuration) is observed for most of the

Zigzag Shaped Magnetic Sensors

January 1, 2004
Author(s)
S da, Willard C. Uhlig, A Kos, Joe Aumentado, Michael J. Donahue, John Unguris, David P. Pappas
Magnetism in zigzag shaped thin film elements is investigated using scanning electron microscopy with polarization analysis, magneto-transport measurements, and micromagnetic simulations. We find that the angle of magnetization alternates along the length

Electron Beam Stimulated Spin Reorientation

May 15, 2003
Author(s)
T L. Monchesky, John Unguris, Robert Celotta
Using Scanning Electron Microscopy with Polarization Analysis (SEMPA), we observed the electron beam induced switching of the magnetic state of epitaxial single-crystal Fe(110) films grown on atomically flat cleaved GaAs(110). For low film thickness the

Direct Observation of Remanent Magnetic States in Epitaxial fcc Co Small Disks

April 1, 2003
Author(s)
C Vaz, L Lopez-Diaz, M Klaui, J Bland, T Monchesky, John Unguris, Z Cui
The magnetic nanostructure of epitaxial fcc Co/Cu(001) circular elements (1.7υm in diameter) has been imaged with scanning electron microscopy with polarization analysis. The disks are obtained by ultrahigh vacuum deposition of the metal films onto a

Magnetic Domain Imaging of Spintronic Devices

January 1, 2003
Author(s)
Robert Celotta, John Unguris, Daniel T. Pierce
A description of high resolution magnetic domain imaging methods of specific use in observing magnetic structure in magneto electronic, i.e., spintronics.

The Magnetic Order of Cr in Fe/Cr/Fe(001) Trilayers

January 1, 2001
Author(s)
Daniel T. Pierce, John Unguris, Robert Celotta, Mark D. Stiles
The temperature dependence of the short period oscillatory coupling in Fe/Cr/Fe(001) whisker trilayers, when analyzed in light of recent theory, provides strong evidence that incommensurate spin density wave antiferromagnetic order is induced in the Cr

Non-collinear Exchange Coupling in Fe/Mn/Fe(001): Insight from Scanning Tunneling Microscopy

December 1, 2000
Author(s)
Daniel T. Pierce, Angela Davies, Joseph A. Stroscio, D Tulchinsky, John Unguris, Robert Celotta
The film growth and morphology of epitaxial Mn films grown on Fe(001) single crystal whiskers measured with scanning tunneling microscopy (STM) provides insight into the mechanism of interlayer exchange coupling in Fe/Mn/Fe(001) trilayers. The proximity

Techniques to Measure Magnetic Domain Structures

September 11, 2000
Author(s)
Robert Celotta, John Unguris, Michael H. Kelley, Daniel T. Pierce
A summary of the current techniques for magnetic domain imaging of materials, including the practical aspects of each technique, the requirements on the sample, the specimen modification allowed and the problems normally encountered. References to more

Magnetic Depth Profiling Co/Cu Multilayers to Investigate Magnetoresistance

May 1, 2000
Author(s)
John Unguris, D Tulchinsky, Michael H. Kelley, Julie A. Borchers, Joseph A. Dura, Charles F. Majkrzak, S. Y. Hsu, R Loloee, W Pratt, J Bass
The magnetic microstructure responsible for the metastable high resistance state of weakly coupled, as-prepared [Co(6nm)/Cu(6nm)] 20 multilayer was analyzed using polarized neutron reflectivity (PNR) and scanning electron microscopy with polarization