Ba<inf>0.85</inf>Ca<inf>0.15</inf>Zr<inf>0.1</inf>Ti<inf>0.90</inf>O<inf>3</inf>/CoFe<inf>2</inf>O<inf>4</inf>/Ba<inf>0.85</inf>Ca<inf>0.15</inf>Zr<inf>0.1</inf>Ti<inf>0.90</inf>O<inf>3</inf>Nanoscale Composite Films with 2-2 Connectivity for Magnetoelectric Actuation

Interfacial strain plays a vital role in determining the coupling strength between the magnetic and electrically ordered phases in magnetoelectric (ME) nanostructures. The interfacial strain and its gradient size in a polycrystalline trilayer ME composite with a specific microstructure were estimated by grazing incident X-ray diffraction (GI-XRD). The average interfacial strain was estimated to have a maximum value of ∼7%, and was found to be relaxed at a length scale of 25-35 nm away from the interface. The optimized gradient size estimated from the trilayer ME composite was utilized to fabricate multilayers with specific periodicities ("Δ") and tested for the inverse piezomagnetic effect to estimate the optimum periodicity required to have enhanced ME coupling. Multilayers with periodicity (∼40 nm) compared to multilayers with relaxed/partial interfacial strain exhibited ∼25 to 26% increment in piezoelectric coefficient (d33) in the presence of a magnetic field. The constraint imposed on polarization by interfacial strain reflects on the enhancement of stiffness and introduces a quicker linear response to the piezoelectric displacement. In contrast, the partially strained and/or strain-relaxed layers exhibited nonlinear responses in polarization switching. The linear piezoelectric displacement in these strain-engineered ME composites makes them a potential candidate for device applications like actuators and transducers.