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.

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.

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.