How we can explain the Cobalt thickness effect on the dielectric permittivity of Co/Ag bilayer film ?
Thanks
Dear Maha:
As a rule of thumb for the optical behavior: the higher the thickness of the Co layer, the higher the optical absorption of the system. Regarding the magneto-optical response, it also increases with the Co thickness (gradual variation of the polar Kerr rotation and ellipticity).
However, when the Surface Plasmon Polariton (SPP) resonance is excited, the behavior changes. If you work with the Kretschmann configuration, the SPP excitation manifests as a reduction on the reflectivity at a specific angle of incidence above the critical angle for total internal reflection. And the magneto-optical signal exhibits a maximum for a specific Co thickness: the one that allows for optimum excitation of the SPP maximizing the electromagnetic field at the level of the Co layer. For thicker Co thickness, the higher optical absorption of the system makes the SPP excitation not optimal anymore and the magneto-optical response decreases.
This phenoma have been extensively studied in Au/Co/Au and Ag/Co/Ag trilayers. You can have a look at these works:
DOI: 10.1103/PhysRevB.76.153402
DOI: 10.1103/PhysRevB.80.125132
The different Co thickness for optimal SPP excitation and therefore maximum MO transverse Kerr signal is due to the different optical constants of Au and Ag.
If this is useful, please check “Recommend”. Thanks
Dear Mr. Jose-Miquel,
I want to thank you very much for your explication. I found it very interesting I still hope to benefit from your professional expertises .
Cordially
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