Orientation Control and Properties of Pb(Zr, Ti)O3 Thin Films Deposited on Ni–Zn-Ferrite for Novel Ferroelectric/Ferromagnetic Memory Applications

Abstract

A novel memory with a ferroelectric/ferromagnetic stacked structure was proposed. Multilevel recording is expected for this novel memory. The principle of ferroelectric recording is the same as that for field effect transistor (FET) ferroelectric random access memories (FeRAMs). The principle of magnetic recording is that the source-drain current is modified by the Lorentz force caused by the remanent magnetization of ferromagnetic thin film. It was clarified that the drain current and source-drain voltage (Id–Vd) characteristics of a Si metal-oxide-semiconductor field effect transistor (MOSFET) was actually modified in an external magnetic field. Such modification was also brought about by the remanent magnetization of a ferromagnetic thin film. To achieve high remanent polarization and remanent magnetization at the same time in the ferroelectric/ferromagnetic stacked structure, we prepared Pb(Zr, Ti)O3 (PZT)/(Ni, Zn)Fe2O4 (NZF) thin films with several crystallographic orientations on Si(001) substrates. The orientations of PZT and NZF thin films were controlled by designing buffer layers between the Si(001) substrate and NZF thin film. It was found that (111)-orientatied PZT on (111)-orientated NZF thin film satisfied both high remanent polarization and remanent magnetization at the same time.