We studied nanoscale elliptical ring shaped NiFe/Cu/NiFe trilayer pseudo-spin-valve structures. The magnetization reversal processes showed simultaneous-reversal single-step transition or double-step transition involving flux closure states. For various aspect ratios (short axis to long axis) and linewidths, transition between single-step and double-step magnetization reversals was measured to form a phase diagram. When the linewidth was reduced, edge roughness became important. Simulations of the magnetization reversal behavior agreed qualitatively with our results.

We investigate a series of Cu-Py-crossed stripe devices in which the contact magnetoresistance behavior exhibits hysteretic loops originating from anomalous Hall effect in Py at the Cu/Py contact area with in-plane magnetization. These highly reproducible hysteretic loops relate directly to the magnetization switching of Py wires at the crossed regions. The nonzero magnitude of resistance difference (ΔR) between the two remnant states at zero Oe depends on the width of Cu by a roughly reciprocal relation, but is independent of that of Py wire. The ΔR ranges between 0.1 ∼ 0.6 mΩ with Cu width of 100 nm ∼ 500 nm and Cu/Py thickness of (65 nm)/(31 nm) ∼ (50 nm)/(20 nm). The results provide understanding of how the Hall voltage is induced and sensed.