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Title: Structure and magnetism in ultrathin iron films
Author: Gray, S. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1996
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Fe films have been grown epitaxially on Ag(001) and GaAs(001) substrates. Ultra high vacuum conditions were used to allow the evolution of structural and magnetic properties to be studied during film growth. Structural characterisation was by LEED and RHEED and in situ magnetic characterisation by longitudinal MOKE and BLS. These techniques were further used to study the effect of Ag and Cr overlayers on 6 and 14 ML Fe films. Some films were capped and further characterised ex situ by longitudinal and polar MOKE, and Kerr spectroscopy. Fe films deposited on Ag(001) were found to cover the substrate after approximately 4 ML had been deposited. Quantitative analysis of the LEED patterns enabled step separations to be estimated. It was found that there was a minimum average step separation at 3 ML Fe. The LEED patterns show pyramids, characteristic of growth dominated by Schwoebel barriers. In situ BLS and ex situ MOKE was used to study the evolution of the cubic and surface anisotropy constants K1 and Ks with thickness. For very low thicknesses K1 becomes just negative. At low temperatures thin Fe films are magnetised normal to the plane of the film. At higher temperatures an apparent gap in the magnetisation at the out-of-plane transition is seen. At higher temperatures still no remanent perpendicular magnetisation is seen. The gap and loss of remanent magnetisation are found to be due to domain formation. Ag deposited on Fe was found to show very little interaction, and all magnetic effects were saturated within 3 ML. Cr deposition on Fe gave rise to changes in the surface anisotropy and magnetisation consistent with the antiferromagnetic nature of Cr with the first layer aligned antiparallel to the underlying Fe. This was seen on rougher Fe films.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available