Overseas Travel Grant: XMCD-PEEM study of the spin structure and spin torque in magnetic nanocontacts at the Advanced Light Source (ALS)

Lead Research Organisation: University of York
Department Name: Electronics


This overseas travel grant application is to seek the support from the EPSRC to cover the travel and accommodation costs of our beam time at the Advanced Light Source (ALS) to study the spin torque effect in magnetic nanocontact, one of the most exciting topics of spintronics. The DTI has stated that, 'by 2015 spintronics technology will be the only way to make electronic devices smaller and more efficient -by then, existing semiconductors and semiconductor materials, like silicon, will have exhausted their capability for miniaturization.' [DTI Global Watch magazine, July /August 2005]. This is a growing interest in the use of spin-polarised current rather than the external magnetic fields to switch the spintronic devices. The current-induced magnetization switching, well known as spin-torque effects, can locally switch a magnetic element to avoid cross-talk and reduce the power consumption. Due to the spin and momentum transfer, the spin-polarised current can move away a domain wall trapped in a magnetic nanocontact, or switch the magnetic sub-layer in a GMR-type nanopillar structure. Over the last few years, there are several Nature and Science papers reporting the discovery of this effect and its great potentials, and during the 52nd Annual Conference on Magnetism and Magnetic Materials last November in Tampa, Florida, there were around 150 invited and contributed presentations on spin-torque effect and its applications. We have been awarded 12 shifts of beamtime at the Beamline at the Advanced Light Source, USA, to study the spin structure and spin torque in magnetic nanocontact using x-ray magnetic circular dichroism in photoemission electron microscopy (XMCD-PEEM) (Proposal Number: ALS-02778, see the attached letter). We have also been awarded a new EPSRC project (EP/G0100641/1) with a PhD student to work on this topic (Note: This new EPSRC doesn't cover the travel and accommodations costs for the ALS beamtime). The 11.0.1 PEEM3 beamline at ALS with a spatial resolution of better than 20 nm offers a superior technique to probe both the spin configuration and orbital moment in magnetic nanocontacts, which is expected to provide unique information to understand the mechanisms of spin-torque effect and domain wall scattering, both depending on the spin-orbital exchange coupling. In specifically during this project in the ALS, we will measuring the spin configurations and spin and orbital moments in FeNi magnetic nanocontacts, and to investigating the dependence of the critical current density and domain wall magneto-resistance nanocontacts sizes in the FeNi nanocontacts.For the future work, we are applying for the beamtime to the Diamond NanoScience beamline (I06), as described in our new EPSRC grant proposal. The experiences to be obtained from our beamtime in ALS as described in this project will help the Diamond's beamline I06 to carry out the work in this new area. Apart from the FeNi to be measured in ALS in this project, we are planning to study both the spin structures and the spin and orbital moments as a function of the magnetic nanocontact size and the film thickness in polycrystalline Ni and single crystal Fe and Co in the Diamond's beamline I06. Our final objective is to determine suitable materials, crystal structures, geometries and sizes of magnetic nanocontacts with the aim to achieve large current-induced resistance changes and low critical current density for spintronics applications.


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