Reducing spin torque switching current density by boron insertion into a CoFeB free layer of a magnetic tunnel junction

The spin torque switching current density is measured for magnetic tunnel junctions containing a CoFeB free layer. We find that the insertion of an ultra-thin boron layer near the free layer/tunnel barrier interface gives rise to an increased resistance-area product and to a reduction in the switching current density. This is attributed to a lower tunneling matrix element near the inserted boron. As a result, the injected current is concentrated within smaller areas of the free layer, which leads to an overall decrease in the switching current density. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704916]