Local Hall measurement of magnetization reversal and magnetic interaction in Fe/Au/Fe trilayer rings

Magnetization reversal process of ring-shaped Fe/Au/Fe pseudo-spin valve is investigated with different Au thickness by local Hall effect (LHE) using semiconductor two dimensional electron gas. The Hall resistance shows clear hysteresis loop with four different transition fields. By comparing the single-layer Fe rings, four steps are due to the onion (voretex)-to-vortex (onion) transitions both in the top and the bottom rings. The LHE measurement enables us to measure the distinct characterization of the magnetization reversal between the top and bottom Fe rings. Magnetic interactions between two Fe rings are measured as a function of Au thickness. The variation of the onion-to-vortex transition field is explained by the displacement of the domain walls in the onion state due to the stray field from the ring edge. The vortex-to-onion transition fields are shifted to the lower field in both Fe layers with decreasing Au thickness due to the reduction of entire magnetostatic energy in PSV rings. One possible explanation is the absorption of the stray field between two Fe rings.