Title: Electric field control of magnetism in multiferroic heterostructures

Abstract:  

Due to this collection of rich electronic phases, the complex oxides offer unparalleled opportunities for investigating correlated electron phenomena and demonstrating new proof-of-concept devices.  Modern magnetic memory technology is faced with issues of scalability and energy consumption as the required electrical current causes significant heating and stray magnetic fields. An ideal solution to this problem would be a magnetic device that can be controlled with an electric field in a capacitor structure as the electric field is well confined and minimal energy is dissipated. One issue is that the switching a magnetic device requires breaking time reversal symmetry, a symmetry that is broken by an applied current or magnetic field but not by an applied electric field. Combined ferroelectrics and magnetic materials, so called multiferroics, open pathways towards the electric field control of magnetism and energy efficient spin-based technologies. While researched for some time, critical challenges in developing new materials with large magnetoelectric coupling that can both scale to device dimension and be fast. Here I will present our results of stabilized Fe1-xGax alloys to boost (by 200-300% relative to bulk) the magnetostriction of Fe1-xGax thin film alloys by extending the phase stability of the A2 phase to higher Ga compositions. Transport-based magnetoelectric characterization of a Fe1-xGax - [Pb(Mg1/3Nb2/3)O3]0.7-[PbTiO3]0.3 (PMN-PT) composite multiferroic heterostructure shows are reversible 90° electrical switch of magnetic anisotropy and a room temperature converse magnetoelectric coefficient of 5.5×10-6 s m-1. The scaling behavior in ferroelectric and multiferroic systems are also unexplored but give rise to key questions on fundamental speed limits to the phase evolution and inherent coupling between order parameters. I will conclude the talk with our recent advancements in studying dynamic behavior in ferroic materials scaled below the domain length.