\textit{In Situ} Electrical Biasing Studies of Magnetoelectric Coupling in La$_{1-x}$Sr$_{x}$MnO$_{3}$-PbZr$_{x}$Ti$_{1-x}$O$_{3}$ Thin Film Oxide Heterostructures

Thin film La$_{1-x}$Sr$_{x}$MnO$_{3}$ (LSMO) -- PbZr$_{x}$Ti$_{1-x}$O$_{3}$ (PZT) magnetoelectric heterostructures possess desirable properties for a range of spintronic applications, but a poor understanding of interfacial coupling dynamics has made them difficult to implement. Here we present a series of magnetization studies utilizing direct \textit{in situ} electrical biasing and switching of PZT polarization. We show that a piezoelectric strain effect gives rise to significant changes in the bulk saturation magnetization of LSMO. We complement these measurements with novel \textit{in situ} polarized neutron reflectometry measurements that reveal the spatial extent of induced magnetization. We then correlate these magnetic measurements with local structural and chemical probes to elucidate a structural basis for the observed magnetic properties. From these results we suggest ways to tune coupling for a particular application and we also propose ways to extend these techniques to other composites.