7/3/2018 Caitlin McCoy
Written by Caitlin McCoy
An Illinois Materials Research Science and Engineering Center (MRSEC) team is investigating antiferromagnetic materials that have been identified as promising candidates to realize next-generation logic or memory devices that operate at much higher speed than traditional devices.
The reason? We caught up with Materials Science and Engineering Professor André Schleife and Electrical and Computer Engineering Professor Matthew Gilbert, who said that fundamental time scales of magnetization dynamics in these materials are thought be two orders of magnitude faster than in ferromagnets.
“At the same time, antiferromagnetic order in these materials cannot be switched with an external magnetic field, which makes them resistant to interference with external magnetic fields,” Schleife said. “However, this also creates a major challenge… a suitable mechanism for fast and efficient intentional switching of antiferromagnetic order needs to be realized.”
Recent experiments and theory have demonstrated that this could be achieved by spin-orbit-torques generated by charge currents and optical excitation by circularly polarized light.
The key goal of “IRG1”, an interdisciplinary research group that is part of the Illinois MRSEC, is to explore coupling of magnetic order, optical fields, electronic excitations, and lattice vibrations to better understand fundamental limits on the control of magnetization dynamics.
“In a recent work, published in Physical Review B, we have investigated a possible voltage-induced switching mechanism in an antiferromagnetic semi-metal that exhibits a (semi)metal-insulator transition,” Gilbert explained. “This transition provides a wide range of resistance choices, which is an important prerequisite for a high-density device integration.”
To better understand this, the team combined theoretical and numerical analysis using a model Hamiltonian (an operator corresponding to the total energy of the system) with first-principles calculations using density functional theory — which, according to Schleife, is a computationally feasible, yet accurate quantum mechanical modeling method used to investigate the electronic structure of materials.
“Based on our work, we demonstrate that the proposed switching mechanism is realizable in a realistic material. In addition, we have also discussed the assumptions and limitations of our model to address possible obstacles in realizing the voltage-induced switching mechanism in antiferromagnetic semi-metals,” Gilbert said. “We envision that a two-terminal experiment that we propose should provide a means to identify a distinct signature of the voltage-induced switching of antiferromagnetic order.”