About Donkoun’s research in Spin transistor and spin torque with MgO barrier:

The spin-transfer torque in ferromagnetic and non-magnetic materials was theoretically predicted by Berger and Slonczewski and it was confirmed in a current perpendicular to the plane (CPP) spin valve structure. The operational principle of a spin torque device is based on the angular momentum conservation: an electron polarized or reflected by one magnetic layer transfers its spin angular momentum to the other magnetic layer. The increasing interests in STT switching devices have heightened the need for lowering critical spin switching current density (Jc0) since smaller Jc0 values enable integration of MTJ with compact complementary metal oxide semiconductor (CMOS) transistors. Additionally, for a given MTJ with a certain area and barrier thickness, a smaller Jc0 value decreases the possibility of tunnel barrier breakdown. Substantial efforts have been made so far to lower spin switching current while preserving high thermal stability, such as MTJs with dual MgO tunnel barriers and with perpendicular magnetic materials. However, further improvements are still needed to accommodate scaling down of STT-based devices. In this project, we focused on the decrease in the spin switching current density with nano-aperture structure into a magnetic tunnel junction.