  The electromotive forces induced by surface acoustic waves (SAWs) are
investigated in ferromagnetic thin films. CoFeB thin films deposited on
LiNbO$_3$ substrates are patterned into Hall-bars to study the acoustoelectric
transport properties of the device. The longitudinal and transverse dc voltages
that develop in the Hall bars, which are parallel and orthogonal to the flow of
the SAW, respectively, are measured under application of an in-plane magnetic
field. The longitudinal voltage scales linearly with the SAW power and reverses
its polarity upon changing the direction to which the SAW propagates,
suggesting generation of a dc acoustic current via the SAW excitation. The
magnetic field has little influence on the acoustic current. In contrast, the
SAW induced transverse voltage shows significant dependence on the relative
angle between the magnetic field and the SAW propagation direction. Such field
angle dependent voltage resembles that of the planar Hall voltage induced by
electric current. Interestingly, the angle dependent acoustic transverse
voltage does not depend on the SAW propagation direction. Moreover, the
magnitude of the equivalent angle dependent acoustic transverse resistance is
more than one order of magnitude larger than that of the planar Hall
resistance. These results show the unique acoustoelectric transport properties
of ferromagnetic thin films.
