Magnetoelectric Coupling by Piezoelectric Tensor Design

J Irwin,M S Rzchowski,S Lindemann,V Vaithyanathan,J J Wang,L Q Chen,D G Schlom,C B Eom,J M Hu,W Maeng

doi:10.1038/s41598-019-55139-1

Abstract

Strain-coupled magnetoelectric (ME) phenomena in piezoelectric/ferromagnetic thin-film bilayers are a promising paradigm for sensors and information storage devices, where strain manipulates the magnetization of the ferromagnetic film. In-plane magnetization rotation with an electric field across the film thickness has been challenging due to the large reduction of in-plane piezoelectric strain by substrate clamping, and in two-terminal devices, the requirement of anisotropic in-plane strain. Here we show that these limitations can be overcome by designing the piezoelectric strain tensor using the boundary interaction between biased and unbiased piezoelectric. We fabricated 500 nm thick, (001) oriented [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-PT) unclamped piezoelectric membranes with ferromagnetic Ni overlayers. Guided by analytical and numerical continuum elastic calculations, we designed and fabricated two-terminal devices exhibiting electric field-driven Ni magnetization rotation. We develop a method that can apply designed strain patterns to many other materials systems to control properties such as superconductivity, band topology, conductivity, and optical response.

Highlights

Magnetoelectric materials systems possess a wide range of applications including non-volatile memories, magnetic field sensors, spintronics, tunable RF circuit elements, tunable optics, and biomedical devices[1,2,3]
The first limitation arises from substrate clamping that greatly reduces the in-plane piezoelectric response of thin films[10,11,12], and the second limitation arises from the in-plane four-fold symmetry of most (001) pseudo-cubic piezoelectrics that precludes the anisotropic in-plane strain necessary for in-plane magnetization rotation
The membrane fabrication process starts from an epitaxial PMN-PT / SrRuO3 bilayer on SrTiO3-buffered Si, and results in a piezoelectric membrane heterostructure on a soft polymer (Polydimethylsiloxane [PDMS]) coated glass slide (Fig. 1, see Materials and Methods for details)

Summary

Introduction

Magnetoelectric materials systems possess a wide range of applications including non-volatile memories, magnetic field sensors, spintronics, tunable RF circuit elements, tunable optics, and biomedical devices[1,2,3]. Composite magnetoelectrics have the largest reported magnetoelectric coupling constants and suitable electric polarizations, magnetic coercive fields, and saturation magnetizations. These characteristics make them highly promising inverse magnetoelectric effect device candidates, but up to this point such devices have been challenging to implement in thin-film form[2,5,6,7]. In this work we design, fabricate, and characterize (001)-oriented, thin-film magnetoelectric membrane heterostructures based on the piezoelectric material [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-PT)[8,9]. By designing the piezoelectric tensor, we overcome previous limitations intrinsic to thin films, and demonstrate perpendicular electric field control of in-plane magnetization at low bias voltages. We demonstrate in-plane magnetization reorientation with out-of-plane electric fields, and develop design principles that can be used to generate specific strain patterns

Methods

Results

Discussion

Conclusion