  . We focused on the interaction between two ferromagnetic cobalt layers
through a non-magnetic titanium layer. The magnetic properties of the structure
were characterized by ferromagnetic resonance technique (FMR). The data were
collected as a function of non-magnetic titanium layer thickness. Co/Ti
multilayer (Ti (50 {\AA})/Co(45 {\AA})/Ti(2-40 {\AA})/Co(40 {\AA})/Ti(100
{\AA}))films were grown onto naturally oxidized p-type single crystal Si (100)
substrate at UHV condition with magnetron sputtering system at room
temperature. The thickness of Ti spacer layer ranges from 2 to 40 {\AA} with 2
{\AA} steps. We did not observe usual optic and acoustic modes; instead we had
two broad overlapped peaks for the films ranged from 6 {\AA} to 40 {\AA}. One
interesting result was the high anisotropic resonance field values for these
films. Exchange coupling between ferromagnetic layers causes shift on resonance
field values but these shifts in our samples were much larger than expected.
This large anisotropic behavior is not clear at the moment. Our theoretical
model was not able to determine a value for the exchange coupling parameter.
One reason can be the close thickness values for Co sublayers. The other reason
can be the Ti non-magnetic layer. If titanium did not grow layer by layer on
cobalt, the cobalt ferromagnetic layers may behave as a single layer. As a
result one cannot observe exchange interaction between ferromagnetic layers
through non-magnetic spacer.
