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Dr. Amanda Petford-Long, October 13th

“Magnetic processes at the nanoscale observed using in situ Lorentz electron microscopy”


Understanding the behavior of nanoscale magnetic structures relies on being able to understand the complex interplay of the energy terms that control this behavior at a local scale. The relative contribution of these energy terms can be modified by parameters such as geometric confinement and interactions between adjacent magnetic nanostructures. In addition, it is important to be able to explore how a magnetic nanostructure responds to an external driving force, such as temperature, and electric or magnetic fields. We use Lorentz transmission electron microscopy (LTEM) combined with in-situ magnetizing, heating/cooling and biasing experiments to elucidate the micromagnetic behavior at the sub-micron scale in nanomagnetic structures. By comparing the experimental and simulated results we gain a detailed understanding of the way in which the various energy terms contribute to the behavior that we observe.

I will focus on two examples: firstly, arrays of nanomagnets patterned on lattices (artificial spin ices (ASIs). I will speak to our research on the behavior of ASIs patterned on 2D quasicrystalline lattices, in which the lack of translational symmetry and the varying coordination number at the vertices at which the magnetic bars meet leads to a heterogeneous energy landscape and to varying magnetic frustration across the lattice, even in the ground state. Secondly on lattices with dimers of two bars at each lattice point.

Secondly on thin films of van der Waals materials that host magnetic skyrmions and other topological spin structures in which we make use of cryoEM to explore the way in which order in the skyrmions lattices evolves and the origin of this behavior



Amanda Petford-Long is an Argonne Distinguished Fellow in the Materials Science Division (MSD) at Argonne National Laboratory in Chicago. In addition to her own research program, she serves as the Division Director of MSD and leads Argonne’s Microelectronics emerging initiative. She has a D.Phil (PhD) in Materials Science from the University of Oxford and a B.Sc in Physics from University College, London. She moved to Argonne in 2005 from the University of Oxford where she was a full professor in the Materials Department. Her research focuses on nanomaterials and a particular emphasis is on magnetic and resistive-switching nanostructures with potential applications in information storage technology, and on the use of in-situ TEM. She has published over 350 scientific papers. She is a Fellow of the Royal Academy of Engineering, the Royal Microscopical Society, and the American Physical Society and is a Professor in the Materials Science and Engineering Department at Northwestern University.