In-Plane Sizes Effects on Magnetoelectric Characteristics of a Ni-PZT Planar Heterostructure

Nowadays, the size reduction of electronic devices based on magnetoelectric (ME) effects is an important task. This will provide an opportunity for the wide integration of ME devices into modern microsystem technology. In this letter, the effects of in-plane sizes of planar heterostructures containing a ferromagnetic Ni film and a piezoelectric lead zirconate titanate (PZT) substrate on characteristics of the direct resonance ME effect are investigated. The Ni films of 10 μm in thickness were electrodeposited on the PZT substrates that were 200-μm-thick and 1.2-23 mm in length. The structures were placed in a permanent magnetic field and excited with an ac magnetic field. The generated ME voltage was measured at frequencies near planar acoustic resonances of the structures. For a 1.2 mm long structure, a frequency of 1380 kHz for in-plane acoustic resonance was achieved. A drop in the amplitude of the ME voltage was observed when the length of the structure became less than a critical value. Various mechanisms are discussed that lead to a voltage drop with a reduction of sizes of the structure, including the demagnetization effect, relaxation losses due to frequency dependence of the capacitance and resistance of the PZT layer, and an increase in acoustic losses.