A novel magnetoelectric memory cell based on bilayer ferroelectric films of (1 − x)[Ba(Zr_0.2Ti_0.8)O₃]–x(Ba_0.7Ca_0.3TiO₃)

We demonstrate that a thin film magnetoelectric memory cell, comprised of Fe₇₀Ga₃₀ sputtered on top of bilayer ferroelectric films which consists of a tetragonal (T) 0.7Ba(Zr_0.2Ti_0.8)O₃–0.3(Ba_0.7Ca_0.3TiO₃) (70BZT–30BCT) film deposited on a rhombohedral (R) 0.3Ba(Zr_0.2Ti_0.8)O₃–0.7(Ba_0.7Ca_0.3TiO₃) (30BZT–70BCT) film. The insertion of rhombohedral layer improves the quality of the films and enhances the piezoelectric properties, which could be attributed to that the ferroelectric domains are tethered only by a soft R under layer, and not by the hard substrate. The working mechanism is that the 70BZT–30BCT layer acquires different strain states when an electric field is applied to it. Mechanical transduction couples this strain to the mechanically coupled Fe₇₀Ga₃₀ layer, which then changes its magnetic anisotropy and thus the magnetoresistance. The high (low) resistance states were realized when different voltages were applied due to the anisotropy magnetoresistance of Fe₇₀Ga₃₀ films. The demonstrated magnetoelectric memory device using resistance as the media and electric field as the writing field shows great promises towards exploring magnetoelectric devices for low-power and high density magnetic data storage applications.