Exchange Bias and Domain Evolution at 10 nm Scales

For a fixed 2 mu m x 2 mu m area of a Co/Pt-CoO perpendicular exchange bias system we image the ferromagnetic (FM) domains for various applied fields with 10-nm resolution by magnetic force microscopy (MFM). Using quantitative MFM we measure the local areal density of pinned uncompensated spins ((UCS)-U-pin) in the antiferromagnetic (AFM) CoO layer and correlate the FM domain structure with the UCS density. Larger applied fields drive the receding domains to areas of proportionally higher (UCS)-U-pin aligned antiparallel to FM moments. The data confirm that the evolution of the FM domains is determined by the (UCS)-U-pin in the AFM layer, and also present examples of frustration in the system.