Speaker
James Analytis began his career in condensed matter physics at Canterbury University and went on to Oxford where he focused on quasi-two dimensional organic superconductors. After researching superconductors at Bristol and Stanford University, he became a staff scientist at the Stanford Institute for Materials and Energy Science. Currently, he leads the Analytis lab at Berkeley, creating new materials and investigating their properties under high magnetic fields, with the use of the National High Magnetic Field Lab’s facilities.
Date
Wednesday July 26th, 10am (USA/Pacific)
Abstract
We report on the magnetoelectric properties of the rare-earth Zintl compound Eu5X2As6, a magnetic semiconductor that displays a complex cascade of different magnetic phases. As a result of extensive geometric and magnetic exchange frustration, we observe a unique competition between long-range order and cluster spin glass physics, modulated by the application of small magnetic fields. The effects of this competition are pervasive, including unusual exchange bias characteristics, and negative colossal magnetoresistance of up to a factor of 6× 10^3. Due to the formation of magnetic clusters far exceeding the typical Eu-Eu exchange energy scale, CMR is observed over a wide range of temperatures up to 60 K with magnetic order setting in only below 10.3 K, into a canted antiferromagnetic order. Finally, low-temperature saturation of resistivity is postulated to derive from current shunting by topological surface states predicted via density functional theory calculations, suggesting that Eu5X2As6 is one of the first reported intrinsic magnetic topological insulators.