Prof. William E. Bailey

William E. Bailey

Associate Professor
Materials Science and Engineering
Dept. of Applied Physics
Columbia University
200 SW Mudd Bldg
500 W 120th St.
New York, NY 10027

tel: (212) 854-3090
web54@columbia.edu

Awards

NSF CAREER Award, 2003: "Atomic-scale engineering and in-situ analysis of materials for spin electronics."

ARO Young Investigator Award, 2002: "Atomic-scale engineering of GHz magnetization dynamics"

Fellowships

NRC Postdoctoral Fellow, 1999-2001: Held: NIST, Boulder CO

ONR Graduate Fellow, 1993-1997: Held: Stanford University

My research interests are in the area of materials for spin electronics. Spin electronics exploits an internal degree of freedom of the electron, the spin, as well as its charge. Starting in 1998, spin electronics has moved from laboratory curiosity to $100B/year industry, implemented in magnetic information storage--hard disks, and future nonvolatile memory--by companies such as IBM, Seagate, and Motorola.

The materials science issues raised by spin electronics represent, to me, some of the most exciting opportunities for the field since its outgrowth from metallurgy. Spin electronics systems use ferromagnetic ultrathin films ~ 1 nanometer thick as a control of the electron spin injected into metals, insulators, or semiconductors of similar thickness. For the first time, atomic structure of individual atomic layers, near heteroepitaxial interfaces, controls device properties.

Some current projects (partial list)

Low Ghz loss in epitaxial ferromagnets

Recently, we have created epitaxial ferromagnetic thin films with the lowest Ghz loss (damping) ever observed in a metallic heterostructure. These films are promising for use in nanoscale spin electronic sensors and integrated RF components for wireless telecommunications.

Element- and layer-resolved magnetization dynamics

We have developed the first element and layer-resolved measurement of magnetization precession. The technique uses a stroboscopic measurement of soft x-ray absorption (circular dichroism), synchronized with applied pulsed magnetic fields. Our present demonstration of 5 ps temporal resoution is the fastest in synchrotron-based magnetization dynamics measurments. Project in collaboration with Dario Arena and Elio Vescovo, National Synchrotron Light Source, carried out at the Advanced Photon Source.

Pumped spin currents for gated bandwidth

Many recent experiments show the interrelationship between spin polarized currents and magnetization dynamics, with most attention focused on spin momentum tranfer (SMT) induced switching. Spin polarized electrons forced into an oppositely magnetized layer exert a torque on the magnetization, causing the second layer to switch, or for smaller current densities, to precess. The inverse process is"spin pumping:" a ferromagnetic layer set into precession becomes a source for spin polarized currents. If the generated torque can oppose the damping of an adjacent layer, precession at one layer can potentially suppress relaxation at another, controlled through input RF power. We are exploring this possibility using a novel characterization technique, dual-frequency ferromagnetic resonance (FMR).

Selected Publications

"Low relaxation rate in epitaxial vanadium-doped ultrathin iron films," C. Scheck, L. Cheng, I. Barsukov, Z. Frait, and W.E. Bailey, Physical Review Letters 98(11) 117601 (2007) (link)

"Low damping in epitaxial sputtered iron films," C. Scheck, L. Cheng, and W.E. Bailey, Applied Physics Letters 88(25) 252510 (2006) (link)

"Weakly coupled motion of individual layers in ferromagnetic resonance," D.A. Arena, E. Vescovo, C.-C. Kao, Y. Guan, and W.E. Bailey, Physical Review B 74(6) 064409 (2006) (link)

"Dual-frequency ferromagnetic resonance,"
Y. Guan and W.E. Bailey, Review of Scientific Instruments 77 (6) (2006) (link)

Complete list