Abstract
Surface plasmon excitations can result from the absorption of light incident on gold films. Adding a ferromagnetic metal, in our case iron, allows the surface plasmon resonance peak energy to be manipulated not only by the free electrons present in metals, but by an external magnetic field as well. Surface plasmon resonance is being used by devices found in industry, however manipulations of the surface plasmon resonance peak energy condition need further studies. Two experimental results are reported in this paper based on thin films of iron on gold/chromium, one based on the thickness of iron and the other with an application of a large 4000 Gauss DC magnetic field. Both of these changes result in a shift in the peak energy of the surface plasmon.
Highlights
One method to observe plasmon behavior is by reflecting light off a thin metallic film and measuring the absorbance of light.[1]
These free electrons oscillate with a plasma frequency ωp that is related to the charge carrier density n by equation 1.2 ωp =
A composition weighted average of these indices based on thicknesses of the materials determined the overall index of refraction for the film. This was correlated to the surface plasmon resonance peak energy which was converted into wavelength from figure 2
Summary
One method to observe plasmon behavior is by reflecting light off a thin metallic film and measuring the absorbance of light.[1] Surface plasmons are the collective oscillations of the free electron charge density excited on the surface of the metallic thin films These free electrons oscillate with a plasma frequency ωp that is related to the charge carrier density n by equation 1.2 ωp =. The rationale behind using gold films is justified by the Drude model related to the dielectric permittivity Metals such as silver, gold and copper have low optical losses which have higher propagating lengths for surface plasmons due to longer collision times.[12] This is more favorable for plasmonic devices, materials like gold or silver have been used in surface plasmon instrumentation. Instead of enhancing the peak by changing the composition of the film as done in our previous study, we manipulate the surface plasmon resonance peak by an external magnetic field
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