Since their discovery less than a century ago, antiferromagnetic materials have found only very limited application, in contrast to ferromagnetic materials. In a typical antiferromaget, the atomic magnetic moments couple in such a way that their directions alternate from one lattice site to the next, resulting in zero net spin and, as a result, an absence of stray fields. Thus the magnetic subsystem of antiferromagnets remains “locked” inside and practically inaccessible by external electromagnetic fields. However, a recent discovery of spin-orbital interaction and spin-Hall effect in heavy metals (like Pt) opened a way to create pure “spin-currents”: fluxes of spin angular momentum. It turned out that with spin-currents the magnetic subsystem of antiferromagnets can be accessed and manipulated. We show that under the spin-current the magnetic sublattices of an anisotropic biaxial antiferromagnet can come into a self-sustained precessional motion, see Figure. The dynamics of this motion are defined by a strong exchange interaction between the magnetic sublattices, which results in the frequency of precession reaching the THz range. The precession of antiferromagnetic sublattices can induce (by an inverse spin-Hall effect) a detectable voltage oscillating with a THz frequency, opening a way to create compact and tunable THz frequency sources.

Ivan Lisenkov, PhD is a postdoc researcher at School of Electrical Engineering and Computer Science, Oregon State University. He received his B.S. and M.S. degrees from the Moscow Institute of Physics and Technology in Russia in 2007 and then received his PhD degree in Radiophysics from the Russian Academy of Sciences in 2010.

After his PhD Dr. Lisenkov, joined the Kotelnikov Institute of Radio-engineering and Electronics of the Russian Academy of Sciences. He worked on the theory of acoustic and spin-waves in composite media and metamaterials. In 2013 Dr. Ivan Lisenkov was invited to join the research group of Prof. Andrei Slavin at Oakland University in Michigan. There he studied linear and nonlinear spin-wave dynamics in ferromagnets and antiferromagnets. In November 2016 he joined Prof. Pallavi Dhagat and Albrecht Jander at School of Electrical Engineering and Computer Science to study nonlinear interactions between acoustic waves and spin-waves in ferromagnets.