Fig. 1
From: Magnetization reversal driven by low dimensional chaos in a nanoscale ferromagnet
Device and free layer energy landscape. a Schematics of nanoscale magnetic tunnel junction consisting of a synthetic antiferromagnet (SAF) reference and a superparamagnetic Co60Fe20B20 free layer separated by an MgO tunnel barrier. b Unit sphere representing the free layer magnetization direction m with contour lines of constant magnetic anisotropy energy. The biaxial magnetic anisotropy energy landscape consists of two energy minima at m parallel to the x-axis, two energy maxima at m parallel to the z-axis, and two saddle points for m parallel to the y-axis. c Schematic illustration of the effect of ac spin torque on thermally activated switching of the free layer. The free layer nanomagnet switching trajectory m(t) must pass through the dark gray band induced by ac spin torque where deterministic magnetization trajectories connect the two potential wells. The presence of this band of chaotic dynamics results in erosion of the boundary between the two potential wells and reduction of the effective energy barrier for thermally activated switching of magnetization between the wells
