Current induced magnetisation switching in asymmetric necked wires

The current induced magnetisation switching of Ni₈₀Fe₂₀ wires patterned with a nano-constriction and asymmetric arm widths is studied. It is found that the magnetic field values at which the domain wall is unpinned are ±190 OE, ±150 Oe, ±130 Oe, ±120 Oe for the samples with asymmetric arm width of 500 nm, 600 nm, 700 nm, and 800 nm, respectively, whilst for the sample with 900 nm arm width no evidence of domain wall pinning is observed. As the domain wall is unpinned by current induced domain wall movement at the critical current density, the anisotropic magnetoresistance contribution is removed giving rise to an increase in resistance, hence the discontinuous resistance change in the I-V measurements.