• 
• 
• 

Exchange biased magnetic vortices

Ferromagnet/antiferromagnet exchange biased nanostructures have critical applications in spin-valve type of spintronic devices which enable nanoscale control of magnetic configurations. There has been a long standing issue on whether the macroscopic exchange bias conventionally determined from the major loop is uniform across the entire sample or just a reflection of the weakest point. Researchers led by Prof. Kai Liu at the University of California – Davis have shed new light on this missing link in a study of exchange biased nanodots whose sizes are chosen to be near the boundary of single domain (SD) and vortex state (VS) reversal modes. The major loop exchange bias is deconvoluted into weighted averages of local bias separately experienced by SD and VS dots, and the relative fraction of such dots are found to be modified by exchange bias. Furthermore, the VS nucleation and annihilation fields exhibit unequal shifts caused by the exchange bias, which provide first experimental demonstration of local, incomplete domain walls and tilted vortex cores in such exchange biased nanostructures. The work was supported by the US NSF (Grant No. DMR-1008791 and No. ECCS-0925626), the AFOSR (Grant No. FA9550-10-1-0409), and the Texas A&M University-CONACyT collaborative research program.

Leave a Comment