Principal Investigator(s): Shan X. Wang & Krishna Saraswat

Sponsor(s): Nanoelectronics Research Initiative, Intel

The phenomenon of spin-transfer torque (or simply spin torque) is first conceptualized by Berger and Slonczewski, and experimentally verified by a group from Cornell University. On one hand, if spins are injected from one ferromagnetic layer to another, the conservation of spin angular momentum favors the second magnetization to be parallel to the first; on the other hand, if spins are reflected from another, the conservation law favors the first magnetization to be antiparallel from the second. Spin-torque-based random access memory (STT-RAM) switches bits by the spin-transfer torque effect, is a promising candidate for a nonvolatile and fast magnetic memory. In this project we will vary MgO thickness and explore novel magnetic electrode structures to achieve the desired properties needed for future generations of STT devices.

Efficiently injecting spin polarized electrons from ferromagnetic materials (FM) into semiconductor (SC) has been one of the major challenges in spintronics. FM/oxide/SC structure is considered as a good candidate for spin injection or detection because the tunnel contact between FM and SC might be ideal for solving the conductivity mismatch problem. We are investigating current (I) vs. voltage (V) characteristics of CoFeB/Ge and CoFeB/MgO/Ge junctions in order to decipher the characteristics of these films and their interfaces, which will pave the way for eventually fabricating spin transistors with efficient spin injector and spin detector.