Magnetic Thin Films and Devices: NSF CAREER AWARDTask 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.
GOAL: To develop a spin-dependent scanning tunneling microscope (STM) to investigate magnetic domains of spin polarized samples.
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).
Magnetic Thin Films and Devices: NSF CAREER AWARDTask 2: Spin Polarized Tunneling MicroscopyR.D. Gomez, University of Maryland, College Park, MD
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.
DIGRESSION: CONTRAST FORMATIONIn general, tunneling current density is a
product of density of occupied and unoccupied states of the tip and sample:
)()( eVEEJ Funocc
Focc
samtip
If tip and sample are polarized:
),(),(),(),( eVEEEE Funocc
Focc
Funocc
Focc
samtipsamtip
Or,
JJJJ ,,
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,magneticcontrast
AFM, sampletexture
MFM, magneticdomains
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.
Magnetic Thin Films and Devices: NSF CAREER AWARDTask 3: Patterned Sub-micron Structures
R.D. Gomez, University of Maryland, College Park, MD
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.