  Magnetostatic surface spin waves (MSSW) excited from a coplanar waveguide
antenna travel in different directions with different amplitudes. This effect,
called nonreciprocity of MSSW, has been investigated by micromagnetic
simulations. The ratio of amplitude of two counter propagating spin waves, the
nonreciprocity parameter {\kappa}, is obtained for different ferromagnetic
materials, such as NiFe (Py), CoFeAl, yttrium iron garnet (YIG), and GaMnAs. A
device schematic has been proposed in which {\kappa} can be tuned to a large
value by varying simple geometrical parameters of the device.
