In a letter published recently in the important condensed matter journal Physical Review Letters, Prof. Aurelien Manchon, Assistant Professor of Materials Science and Engineering, and co-author Dr. Xuhui Wang, discuss new theoretical predictions that contribute to the understanding of how electrical currents control magnetization direction, a hot topic in the rapidly developing field of ‘Spintronics’.
Spin Electronics, or ‘Spintronics’, is the field that marries conventional electronics with magnetism, where the magnetic configuration of nanodevices controls the current flowing in it. One of the fundamental effects, coined as Giant Magnetoresistance (GMR), enables ultrahigh storage density, beating the celebrated Terabit/in2 limit. This technology is presently utilized by Prof. Jurgen Kosel, Assistant Professor of Electrical Engineering here at KAUST, for bio-sensor applications.
The reciprocal mechanism, so-called ‘spin transfer torque’, allows for the manipulation of the magnetic configuration by injecting large current densities into the device. This effect is now exploited in promising applications such as non-volatile memories (MRAM – Fig. 1(a)) and radio-frequency oscillators. Although not on the market yet, this technology has been identified as a potentially viable way to replace DRAM (dynamic random-access memories) and to perform reprogrammable logic in low power consumption systems. However, the current technology is limited by the complexity of the multilayer stack needed to achieve a spin-valve (Fig. 1(b)).
A recent development in the field was the theoretical prediction by Prof. Manchon and Dr. Zhang that an appropriately designed spin-orbit interaction (a fundamental connection between the spin and the electron propagation direction) could replace the need for a polarizer and allow the electrical control of the magnetization of a single ferromagnet. This would simplify the architecture and performances of devices significantly. High-end research in the field has subsequently confirmed the existence of the so-called ‘spin-orbit-induced torque’. Prof. Manchon and his team’s latest work paves the way to a better understanding of this effect.