  We propose a method to control surface phonon transport by weak magnetic
fields based on the pumping of surface acoustic waves (SAWs) by
magnetostriction. We predict that the magnetization dynamics of a nanowire on
top of a dielectric films injects SAWs with opposite angular momenta into
opposite directions. Two parallel nanowires form a phononic cavity that at
magnetic resonances pump a unidirectional SAW current into half of the
substrate.
