  Here we demonstrate the enhancement of the transverse magneto-optical Kerr
effect (TMOKE) signal, in the Otto configuration, due to surface plasmon
resonance. We present an architecture where the low index dielectric has a
variable thickness. This allows the plasmon resonance to be tuned, depending on
the magnetic sample and thus be utilized to enhance the MOKE signal of samples
separated from the plasmonic device. We have achieved this by using air as low
index dielectric where the evanescent wave extends, preceding to excitation of
surface plasmons. The magnetic sample under consideration is a thin layer of
cobalt coated by an ultrathin silver layer, on a silicon substrate (Ag/Co/Si).
The sample is brought close enough to the prism//Air interface, allowing
surface plasmon excitation in the air/Ag interface. This leads to an increase
of the TMOKE signal up to ~ 2 per mil with respect to the incident light. This
is about 8 times the traditional MOKE signal in the absence of plasmons. This
is comparable with previous works using the Kretschmann-Raether configuration.
This should find applications in MOKE-related technology by increasing its
sensitivity to about one order of magnitude and allowing the magnetic sample to
be separated from the plasmonic resonance device.
