Abstract

Conventional CMOS based logic and data storage devices require the shuttling of electrons for data processing and storage. As these devices are scaled to increasingly smaller dimensions in the pursuit of speed and storage density, significant energy dissipation has become a center stage issue for the microelectronics industry. Instead, a new paradigm for logic and memory has emerged harnessing the long-range order of charge, spin, and strain in materials (so called ferroic materials) that exhibit collective thresholding switching and non-volatility which enables new scaling trends in energy dissipation per operation. My group investigates and engineers the interplay between spin, charge, lattice, and orbital degrees of freedom in intrinsic and artificial systems for novel device functions. Here I will discuss the advances we have made in composite multiferroics composed of a magnetostrictive ferromagnet and a piezoelectric ferroelectric which hold promise for magnetic field sensors and energy efficient beyond-CMOS logic by harnessing magnetoelectric transduction. Enhancing device performance requires highly magnetostrictive materials, however, relatively little attention has been given to engineering magnetostriction in thin films. Here I will present a novel means to boost the magnetostriction, and by extension the magnetoelectric coefficient, by extending the phase stability of a chemically disordered metastable phase of Fe1-xGax thin film alloys. 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 large room temperature converse magnetoelectric coefficient of ~2×10-5 s m-1. I will conclude the presentation with advances toward realizing sub 250 mV write voltage and sub 100 aJ energy dissipation per operation performance.

 

Bio

John Heron was awarded B.S. from UC Santa Barbara in 2007 where he studied magnetic semiconductors in the lab of Prof. David Awschalom. For masters and Ph.D. degrees (awarded in 2011 and 2013), he investigated magnetoelectric switching of thin film BiFeO3 under the mentorship of Prof. Ramamoorthy Ramesh at UC Berkeley. Heron received the Ross N. Tucker award for superior work and scholarship in the characterization, development and/or use of semiconductor, magnetic, optical or electronic materials by a graduate student or students pursuing such areas of inquiry at the University of California, Berkeley in 2013. As a postdoc in the lab of Prof. Schlom, Heron investigated magnetoelectric switching in novel composite multiferroic heterostructures. Since Jan. 2016, John Heron is now Assistant Professor of Materials Science and Engineering at the University of Michigan. The Heron group designs ferroic materials for energy efficient devices. He is best known for his work on the pulsed laser deposition thin film ferroic and multiferroic oxides and the characterization of magnetoelectric and multiferroic materials. Particular interest resides in interface, spin, structure, and charge effects that occur in layered structures with ferroic materials, such as (anti)ferromagnets, (anti)ferroelectrics, and multiferroics. He was a recent recipient of the NSF CAREER award to investigate novel high entropy oxide materials as prospective correlated electron systems with vast tunability for new memory elements, steep slope transistors, and selectors.

 

Host

Sumeet Kumar Gupta, guptask@purdue.edu