Lesley Cohen – Chair of the Advisory Board
Title: Non-collinear Mn3NiN Antiferromagnets

Abstract: Antiferromagnets (AFM) hold interest because of their potential for application in high density, high speed spintronic devices, as  an active layer and also as a component in superconducting S/AFM/S Josephson Junctions. Frustrated non-collinear antiferromagnets offer additional attractive functional properties due to their magnetic space group symmetry. Stimulated first by the prediction of piezomagnetism we embarked on a growth program of Mn3NiN films on various perovskite substrates by pulsed laser deposition. In this talk I will review the evidence for piezomagnetism and our observation of the anomalous Hall effect. We use scanning imaging of the anomalous Nernst effect to provide information about domain structure in our films. The phase diagram of magnetic order with biaxial strain in this family of materials predicts that compressively strained films should support a collinear ferrimagnetic phase as shown in the figure below. I will discuss the properties of this phase and implications and the magneto-optical properties crossing from the antiferromagnetic to ferrimagnetic phase.

Speaker Bio: Lesley Cohen is a Professor of Solid State Physics at Imperial College London. Her research focuses on quantum interference for organic thermoelectric, energy-efficient solid-state caloric cooling, competing for exchange antiferromagnets for spintronics and long-range triplet superconductivity. She is currently the Consul for the Faculty of Natural Sciences and Education at Imperial College and recently stepped down as head of Experimental Condensed Matter. She received the Imperial College Julia Higgins Award for her contribution to the promotion and support of women in science and remains committed to equality and diversity within STEM.

Dr. Cohen has served on numerous Boards including Superconductivity, Science and Technology; Imperial College Consultants ICON; the Education Board for the Institute of Physics; Kings College London Science Advisory Board; and the External Advisory Board of IFW Dresden and the EPSRC Materials Strategic Advisory Technical Panel.