Fig. 6: Contact lead magnetoresistance and transition variation.
a Major resistance (R) vs. in-plane magnetic field (H) loop measured on the contact leads at 0.3 K for the device with Nb thickness dNb = 21 nm (μ0 is the magnetic permeability in a vacuum). For this device only, there is a negative (parallel state is higher resistance) magnetoresistance response in the contact leads at the measurement temperature. Inset: for all other devices, the leads are superconducting below the contact lead transition, and show no magnetoresistance response at T/Tdevice = 0.3, where T is temperature and Tdevice is the onset temperature of the device transition. b R(T) curves from two devices on the same substrate dNb = 57 nm, normalised by their normal state resistance for comparison. The difference between the temperature of contact and device transitions varies in an unknown manner, and can be small enough that the two transitions are indistinguishable. Inset: Tdevice vs. nanopillar area, for a device showing the superconducting spin valve effect (dNb = 25 nm, dark blue) and a device showing quasiparticle giant magnetoresistance (dNb = 37 nm, light blue). Error bars represent measurement uncertainty.
