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.