Spin-transfer torque switching at ultra low current densities
  The influence of the tantalum buffer layer on the magnetic anisotropy of perpendicular Co-Fe-B/MgO based magnetic tunnel junctions is studied using magneto-optical Kerr-spectroscopy. Samples without a tantalum buffer are found to exhibit no perpendicular magnetization. The transport of Boron into the tantalum buffer is considered to play an important role on the switching currents of those devices. With the optimized layer stack of a perpendicular tunnel junction, a minimal critical switching current density of only 9.2 kA/cm$^2$ is observed. As of today, this value is the lowest reported value for current-induced magnetization reversal. 
Johannes Christian Leutenantsmeyer, Vladyslav Zbarsky, Steffen   Wittrock, Marvin Walter, Patrick Peretzki, Henning Schuhman...
cond-mat.mtrl-sci