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Fazel Tafti: A New Paradigm for Colossal Magnetoresistance and Nonlinear Hall Effect
February 17 @ 10:00 am - 11:00 am
Meeting ID: 684 7017 3961
Speaker: Fazel Tafti, Boston College
Materials with strong magneto resistive responses are the backbone of spintronic technology, magnetic sensors, and hard drives. Among them, manganese oxides with a mixed valence and a cubic perovskite structure stand out due to their colossal magnetoresistance (CMR). A double exchange interaction underlies the CMR in manganates, whereby charge transport is enhanced when the spins on neighboring Mn3+ and Mn4+ ions are parallel. Prior efforts to find different materials or mechanisms for CMR resulted in a much smaller effect. In this talk, I present the observation of an enormous CMR at low temperatures in EuCd2P2 without manganese, oxygen, mixed valence, or cubic perovskite structure. EuCd2P2 has a layered trigonal lattice and exhibits antiferromagnetic ordering at 11 K. The magnitude of CMR (104%) in as-grown crystals of EuCd2P2 rivals the magnitude in optimized thin films of manganates. The magnetization, transport, and synchrotron X-ray data suggest that strong magnetic fluctuations are responsible for this phenomenon. The realization of CMR at low temperatures without heterovalency leads to a new regime for materials and technologies related to antiferromagnetic spintronics.
Fazel Tafti completed his PhD at the University of Toronto with Prof. Steven Julian. His thesis was focused on developing transport experiments under ultrahigh pressures in diamond anvil cells. His first postdoc position at the University of Sherbrook with Prof. Louis Taillefer was focused on the thermal conductivity and thermoelectric measurements in iron-based superconductors under intense magnetic fields. He then changed fields from physics to chemistry and completed a second postdoc at Princeton University with Prof. Bob Cava. His research was focused on the chemical synthesis of topological and magnetic materials. He has been an assistant professor at Boston College (physics department) since 2016. His lab is interdisciplinary between physics, chemistry, and materials science.