Magnetic Thin Films and Devices: NSF CAREER AWARD

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Magnetic Thin Films and Devices NSF CAREER
AWARD Task 1 Surface Morphology and Magnetic
Structure R.D. Gomez, University of Maryland,
College Park, MD
GOAL To correlate microstructure and magnetic
properties of Co on Si(100) as a function of
thickness.
APPROACH A UHV-system with deposition and
in-situ scanned probe microscope capability is
used to make cobalt arrays with thickness
gradient at the pattern edges. A novel in-situ
shadow mask is developed.

• ACCOMPLISHMENTS
• First atomically-resolved systematic correlation
  of grain-size and thickness.
• First UHV-MFM observations of domain boundaries
  at edge

• PUBLICATIONS
• UHV MFM/STM study of in situ structured Cobalt
  films on Si(001), M. Dreyer and R. D. Gomez,
  Joint MMM/Intermag 2001 Conference, submitted.

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Magnetic Thin Films and Devices NSF CAREER
AWARD Task 2 Spin Polarized Tunneling
Microscopy R.D. Gomez, University of Maryland,
College Park, MD
GOAL To develop a spin-dependent scanning
tunneling microscope (STM) to investigate
magnetic domains of spin polarized samples.
DIGRESSION CONTRAST FORMATION
In general, tunneling current density is a
product of density of occupied and unoccupied
states of the tip and sample
APPROACH Use standard STM with special CrO2
coated tip, on 200 nm perpendicularly magnetized
NiFe (permalloy) sample. CrO2 is 100 spin
polarized, Permalloy is 30. Correlate with
magnetic structure obtained using magnetic force
microscope (MFM).
If tip and sample are polarized
Or,
MILESTONE Successful coating of STM tip, using
high temp CrO3 decomposition on O2 reactor
chamber.
ACCOMPLISHMENT Successful imaging of domains in
permalloy using CrO2 tip, possibly first
observation of domains of NiFe using spin
polarized probe.
STM with CrO3 tip, magnetic contrast
AFM, sample texture
MFM, magnetic domains
PUBLICATION Development of Spin Polarized
Scanning Tunneling Microscopy for Magnetic Domain
Imaging, J. Flory, M. Dreyer, W. Egelhoff, T.
Egelhoff and R.D. Gomez, in prep.
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Magnetic Thin Films and Devices NSF CAREER
AWARD Task 3 Patterned Sub-micron
Structures R.D. Gomez, University of Maryland,
College Park, MD
GOAL To understand the domain configuration and
switching characteristics of epitaxially grown
Cobalt/MgO.
APPROACH Use MFM in the presence of applied
external field on patterned films fabricated at
Stanford University by Prof. R.L. White and S.
Ganesan.

• RESULTS
• MFM images show exclusive domain configuration
  with shape and crystal anisotropy easy axes are
  parallel (S1).
• MFM images show single and bidomain stable
  configurations when shape and crystal anisotropy
  axes are orthogonal (S2).
• For S1, Hc 2500 Oe, single domain reversal.
• For S2, Hc 1800 Oe, reversal via single and
  intermediate bidomain states.