  We demonstrate that the magnetization of a ferromagnet in contact with an
antiferromagnetic multiferroic (LuMnO3) can be speedily reversed by electric
field pulsing, and the sign of the magnetic exchange bias can switch and
recover isothermally. As LuMnO3 is not ferroelastic, our data conclusively show
that this switching is not mediated by strain effects but is a unique
electric-field driven decoupling of the ferroelectric and ferromagnetic domains
walls. Their distinct dynamics are essential for the observed magnetic
switching.
