Probing magnetic interfaces using standing spin wave modes

Rhet Magaraggia

    Research output: ThesisDoctoral Thesis

    500 Downloads (Pure)

    Abstract

    [Truncated abstract] Ferromagnetic resonance is a technique which uses coherent spin precession, or standing spin wave modes, to infer the local magnetic conditions in a ferromagnet. This dissertation demonstrates how observation of multiple standing spin wave modes can be used to probe the properties of magnetic interfaces. Ferromagnetic resonance experiments using a broadband vector network analyser are described in the study of (1) exchange biased interfaces, (2) multiferroic interfaces and (3) patterned films (periodic ferromagnet/air interfaces). Calculations are also presented that relate the experimentally measured resonance frequencies to properties of the material interfaces. Using coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin wave thickness mode in Ni80Fe20/Ir25Mn75 exchange biased bilayers was studied for a range of Ir25Mn75 thicknesses. It is shown that pinning of the standing mode can be used to amplify, relative to the fundamental resonance, frequency shifts associated with exchange bias. The shifts provide a unique `fingerprint' of the exchange bias and can be interpreted in terms of an e ective ferromagnetic film thickness and ferromagnet/antiferromagnet interface anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic Ir25Mn75 thicknesses, and the onset of bias is correlated with changes in the pinning elds. The pinning strength magnitude is found to grow with cooling of the sample, while the effective ferromagnetic film thickness simultaneously decreases.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2011

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