In English

Nanoferromagnets in the focus of plasmon nanoantennas

Lavinia Ghirardini
Göteborg : Chalmers tekniska högskola, 2014. 44 s.
[Examensarbete på avancerad nivå]

Plasmonics is the field of science that studies light-matter interaction. Collective oscillations of electrons at the surface of metals, resulting from an electromagnetic excitation, are responsible for plasmonic phenomena. In metallic nanostructures, these oscillations confine and enhance an electromagnetic field at a sub-wavelength scale, thus having a huge impact on enhanced sensing and spectroscopy applications. Moreover, plasmonics has been also used to enhance weak magneto-optical (MO) effects in magnetic materials. Magneto-optical phenomena are interactions between a magnetic field in a medium and an electromagnetic wave propagating through it [1], resulting in a rotation of the polarization plane and a change in the ellipticity of the polarization state. Magneto-optically active materials have nowadays found applications in a variety of contexts, such as magnetization imaging [2], telecommunication [3], sensors and data storage [4]. Current research focuses on the development of materials with large MO activity to improve the performance of these devices and expand their applications. Since an important factor in integrated technology is size, scaling the dimensions of MO components while preserving the readability of their signal is a crucial requirement. Since the MO response of a material is related to the optical field inside it, plasmonics can allow for its control and manipulation. The interplay between plasmons and magneto-optically active elements has been an important research topic in the field of magnetoplasmonics [5, 6]. Driven by such a research trend, fast, reliable and sensitive MO characterization tools are required in magnetoplasmonics. Conventional systems like the MOKE optical setup, based on frequency modulation methods, are expensive and rather time consuming [7]. This is especially cumbersome in the investigation of small signals which require, in addition, long detector integration time. Here we develope a simple, fast, sensitive and broadband spectrometer-based plasmonic and MO characterization tool. With this tool, which allows small MO signal detection from nanostructures in ambient conditions [8], we study hybrid Au-Fe magnetoplasmonic nanoantennas with different compositions. Evolution of the MO signal when changing the relative amount of the two materials is assessed. We study the extinction spectra and MO response of both the pure Au and hybrid Au-Fe magnetoplasmonic systems. The trend studied is also compared to that of continuous Fe reference films. Our aim is to assess whether these hybrid structures, combined with the use of our detection scheme, are suitable to provide the reduction of the size of the magneto-optical active material without losing the ability to read MO signal from these nanostructures.

Nyckelord: magnetoplasmonics, nanoantenna, nanoferromagnet, Faraday rotation

Publikationen registrerades 2015-01-02. Den ändrades senast 2015-01-02

CPL ID: 209388

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