William Bailey

ASSOCIATE PROFESSOR AND CHAIR OF THE MATERIALS SCIENCE & ENGINEERING PROGRAM COMMITTEE

Office: 1140 S.W. Mudd
Mail: 200 S.W. Mudd, Mail Code: 4701
New York, NY 10027

Tel212-854-3090

Our research is on magnetic thin films and heterostructures.  Modern ultrahigh vacuum deposition techniques have made it possible to create 'heterostructures,' ultrathin films (dozens of atoms thick, or thinner) of one material stacked upon another; composition can be controlled routinely to the level of ~three atomic layers, with the potential for control of single monolayers.  Heterostructures of ferromagnets with other sorts of materials (metals, insulators, semiconductors) offer entirely new functional properties due to the presence of the interface, going far beyond a simple averaging of the two components. 

Research Interests

NANOSCALE MAGNETIC FILMS AND HETEROSTRUCTURES, MATERIALS ISSUES IN SPIN-POLARIZED TRANSPORT, MATERIALS ENGINEERING OF MAGNETIC DYNAMICS

Research Areas

Materials

A canonical example of a new property engineered in a heterostructure is giant magnetoresistance (GMR) in ferromagnet/noble metal heterostructures, topic of the 2008 Nobel Prize in Physics for Albert Fert and Peter Gruenberg.  (I have slides from a short presentation of the work involved in the prize, prepared for a general audience, here  (pdf).)  The key idea is that the spin of the electrons which carry charge in a conductor can be controlled through the magnetization.  This property had direct application as a magnetic field sensor in magnetic recording heads; GMR went from first laboratory discovery (1988) to incorporation as a 'spin valve' in mass produced magnetic recording heads (1998) in just 10 years, something of a record in applied science.

Many new spin-transport-related phenomena have been discovered in the intervening years, with spin torque transfer (and magnetic random access memory, MRAM) devices serving as a focal point.  A relatively new direction for these studies, and one which has interested my group particularly in the past several years, is the possibility of controlling the flow of 'pure' spin currents (without charge, or electrical currents) in ferromagnetic heterostructures.  

The particular specialty of our lab is on high-speed / high-frequency magnetization dynamics in sheet-level films.  We have developed some unique tools in magnetic materials deposition (UHV sputtering; see picture of chamber above) to optimize dynamical properties, and ferromagnetic resonance (FMR) characterization of films in some novel configurations, in our labs at Columbia.  In collaboration with other groups, we have extended FMR to synchrotron pump-probe measurements, which allows us to probe the dynamics of different constituents of heterostructures at GHz frequencies.

The work done in our group is primarily experimental, with quantitative models (usually phenomenological) often used to interpret phenomena in better-developed materials systems.  The research area offers opportunities to work in materials development, fundamental science, and applications in magnetic information storage

Honors & Awards

  • NSF CAREER (2003)
  • ARO Young Investigator (2002)

Education

  • M.S 1995, Ph.D 1999, Stanford University (Materials Science; S.X. Wang)
     
  • Sc.B., B.A. 1993, Brown University (Engineering, Political Science). Graduated with highest honors: Phi Beta Kappa, Tau Beta Pi, Sigma Xi.

Professional Experience

NRC Postdoctoral Fellow, National Institute of Standards and Technology, Magnetic Technology Division, Boulder CO 1999-2001

Select Publications

Nearly isotropic spin-pumping related Gilbert damping in Pt/Ni81Fe19 /Pt
Wei Cao, L. Yang, S. Auffret, W.E. Bailey
Physical Review B (Condensed Matter) 99 094406 (2019)
(pdf) (journal) (cond-mat)

Characterization of spin relaxation anisotropy in Co using spin pumping
Yi Li, Wei Cao, W.E. Bailey
Physical Review B (Condensed Matter) 94 174439 (2016)
(pdf) (journal) (cond-mat)

Phase-resolved imaging of edge-mode spin waves using scanning transmission x-ray microscopy
Cheng Cheng, Wei Cao, W.E. Bailey
Journal of Magnetism and Magnetic Materials 
(pdf) (journal) (cond-mat)

Spin-pumping damping and magnetic proximity effect in Pd and Pt spin sink layers
M. Caminale, A. Ghosh, S. Auffret, U. Ebels, K. Ollefs, F. Wilhelm, A. Rogalev, W.E. Bailey
*Editors' suggestion (link)
Physical Review B (Condensed Matter) 94 014414 (2016) (pdf) (journal) (cond-mat)

Large spin pumping effect in antisymmetric precession of Ni79Fe21/ Ru/ Ni79Fe21
H. Yang, Y. Li, W.E. Bailey
Applied Physics Letters 108 242404 (2016) (pdf) (journal) (cond-mat)

Wavenumber-dependent Gilbert damping in metallic ferromagnets
Yi Li, W.E. Bailey
Physical Review Letters, 116 117602 (2016)  (pdf)  (journal)  (cond-mat)

Static and dynamic magnetization of alloy gradient nanowire
Haozhe Yang, Yi Li, Min Zheng, Wei Cao, W.E. Bailey, and Ronghai Yu
Scientific Reports, 6 20427 (2016)  (journal)