Methods of Manipulating and Dynamics of Ferroic Order in BiFeO3*

With room temperature coupling between magnetic and electric degrees of freedom, BiFeO3 (BFO) has attracted much attention as a leading candidate for magnetoelectric applications. There has been extensive work studying quasi-static magnetoelectric coupling in BFO, but the magnetoelectric coupling dynamics, fundamental speed limits, collective excitations, and intrinsic mechanisms of switching have yet to be explored. Here we explore the switching dynamics of various ferroic orders in BiFeO3 and coupled BiFeO3/Ferromagnetic heterostructures as well as investigate ways to excite and manipulate low-energy excitations of ferroic order.
As the first step in understanding magnetoelectric dynamics, we study time-domain switching dynamics of the ferroelectric state. Using short electrical pulses with rise time ~100ps and pulse widths of the order of 10ns, we are able to probe the switching of the ferroelectric state on timescales much shorter than previous studies. The data reveal low-nanosecond switching, faster than any formerly reported switching times in (La-doped) BFO. We reveal new insight into the ferroelectric switching process in capacitor device structures and analyze switching in the context of magnetoelectric coupling.