Surface magneto-plasmons in magnetic multilayers - Walther ...

Section 2.4
Simulation of the reflectivity of surface plasmons 25
2.4.1 Surface plasmons in different materials
It is evident from Fig. 2.9 that there is a sharp surface plasmon resonance in silver.
A similar analysis of other metals yields optimal layer thicknesses for Au, Ni, Co
and are dAu,opt = 47 nm, dNi,opt = 15 nm, and dCo,opt = 12 nm as shown in Fig. 2.11.
It shows that the optimal layer thickness for the magnetic materials Ni, and Co
p (θS P P )
R
1 .0
0 .8
0 .6
0 .4
0 .2
0 .0
1 .0
0 .8
0 .6
0 .4
0 .2
(a ) ε A u = -1 2 .1 + 1 .4 2 i
(b )
1 5 n m
A u
4 7 n m
ε N i = -1 0 .4 + 1 5 .3 4 i
N i
0 .0
0 2 0 4 0 6 0 8 0 1 0 0
(c )
1 2 n m
la y e r th ic k n e s s [n m ]
ε C o = -1 2 .9 + 1 8 .9 5 i
C o
1 .0
0 .8
0 .6
0 .4
0 .2
0 .0
0 2 0 4 0 6 0 8 0 1 0 0
Figure 2.11: Simulation results for the reflectivity at θSPP plotted versus the layer thickness
of (a) Au, (b) Ni , and (c) Co. The minimum corresponds to the optimal layer
thickness which is for gold 47 nm, for nickel15 nm, and for cobalt 12 nm.
(15 nm, and 12 nm) are much smaller than those for the noble metals Au and Ag
(47 nm, and 46 nm). Calculating the optimal layer thickness with Eq. (2.49) yields
dAg,opt = 47.9 nm, dNi,opt = 15.7 nm, and dCo,opt = 13.3 nm. The deviation between
calculated and numerically values can again be explained by the resolution limit of
the simulation. Like mentioned before the step size of the simulation is 0.1 ◦ . An
other reason for the deviation might be that Eq. (2.49) is only an approximation.
The R p curves of the three materials for the respective dopt are shown in Fig. 2.12. For
the noble metal gold, a clear surface plasmon resonance at θSPP = 43.8 ◦ can be seen.
The R p (θ) evolution shows a similar behaviour like for a silver layer. In contrast, the