Switching behavior of individual pseudo-spin-valve ring structures

In this work, focused magneto-optic Kerr-effect magnetometry, magnetoresistance measurements, and three-dimensional micromagnetic simulations are combined to build a detailed picture of the magnetic switching behavior of micron-scale pseudo-spin-valve ring elements. We find that the reversal of the ring magnetization is dominated by the magnetostatic interaction of the higher magnetic-moment cobalt layer, which nucleates reverse domains in the NiFe free layer, causing it to switch in a manner that would not be possible in a single-layer ring. Measuring single pseudo-spin-valve rings has allowed the resolution of fine details in hysteresis loops, so that small differences between the magnetic states and switching of nominally identical elements can be observed. Furthermore, the high signal to noise ratio of the magnetoresistance measurements allows single-switching events to be observed in the structures. Using this technique we observe a range of phenomena involving both stable and metastable configurations of the ring, which would have been obscured in field-cycle-averaged data.