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NANOMAGNETIC PROPERTIES INVESTIGATED BY NEW MAGNETIC-SENSITIVE LOCAL PROBE TECHNIQUES

Objective


Tip development concentrated on the following materials: semiconductors (spin polarised GaAs probes), ferromagnetic materials and antiferromagnetic materials. Test samples providing a wide range of magnetic properties included Fe(3)O(4), Fe whiskers, garnet films, permalloy films, exchange coupled multilayers, epitaxial magnetic films (Fe and Co on Cu(111)), hard disk material, Ba-ferrite, Co-Cr films, Cr, Fe and Gd films on W(110). They all have been characterised including their structural, topographic and magnetic properties.
SP-STM was tested on thin ferromagnetic Gd-films on W(110) with Fe-covered probe tips. Two peaks in the differential conductivity dI/dU at positive and negative sample bias allowed to map the domain structure of the sample surface with a typical domain size of 100nm with a resolution well below 20 nm. However, we see no physical resolution limit down to the atomic scale. Spin-polarised STM with GaAs tips was developed using cobalt films grown in-situ onto textured Au(111). We observed a polarisation modulation that, when recorded over a scan area of 0.5 um{2}, showing small stripe-shaped domains.
High resolution MFM was achieved by developing magnetic super-tips, where the magnetic material is limited to a small particle of (50nm)(3) using a newly developed nanolithographical method. Not only the spatial resolution could be enhanced, reaching values well below 100 nm, the reduced stray field of the probes enabled also non-destructive high resolution imaging of very soft magnetic samples like garnet films or permalloy thin films. For further development of MFM into a EFM the different force contributions have to be understood, quantified and separated by their different tip-sample distance dependence.
This proposal associates four laboratories experienced in research and development of new scanning probe techniques, an industrial producer of scanning probe equipment, an SME producing probes, and three large industrial companies who are the end users of such an equipment.

The first aim is to develop magnetically sensitive scanning probe techniques which would allow magnetic imaging with ultimate resolution down to the atomic scale. These techniques are : spin-polarised scanning tunnelling microscopy, scanning resonance microscopy and exchange force microscopy..

The techniques use a common scanning method but different magnetic probes and they are therefore sensitive to different physical properties. Parallel development of the three techniques will allow a realistic assessment of their specific sensitivity and optimum development of each of them. The second aim of the project is to use the developed techniques to study magnetic domain walls to improve understanding of the mechanisms governing domain formation and domain wall pinning. These are key factors for perfecting magnetic materials and developing applications in magnetic information storage. The partnership structure allows immediate implementation by the industrial partners of the instrumentation developed with a view to manufacturing the new equipment and implementation of the results on studies of nanodomain with the view to improve performance of magnetic materials.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIV NIJMEGEN
Address
P.o. Box 9010
6500 GL Nijmegen
Netherlands

Participants (3)

Forschungszentrum Jülich GmbH
Germany
Address
Wilhelm-johnen-straße
52405 Jülich
UNIV DUBLIN
Ireland
Address
Trinity College / Univ Dublin
N/A Dublin 2
UNIVERSITY OF HAMBURG
Germany
Address
Jungiusstrasse 11
20355 Hamburg