  Micron scale ferromagnetic tubes placed on the ends of ferromagnetic CoTaZr
spin waveguides are explored in order to enhance the excitation of Backward
Volume Magnetostatic Spin Waves. The tubes produce a closed magnetic circuit
about the signal line of the coplanar waveguide and are, at the same time,
magnetically contiguous with the spin waveguide. This results in a 10 fold
increase in spin wave amplitude. However, the tube geometry distorts the
magnetic field near the spin waveguide and relatively high biasing magnetic
fields are required to establish well defined spin waves. Only the lowest
(uniform) spin wave mode is excited.
