Inhomogeneous spin injection and detection in the lateral FM/Au/FM spin valve device

Effective spin injection to nonmagnetic material gives rise to spin accumulation at anti-parallel magnetic configuration of two FM electrodes. We performed nonlocal measurement with different voltage and current probe configurations on the lateral Py/Au/Py spin valve devices in order to address the cause of non zero base resistance as well as a large difference of non local signal depending on the location of injecting or detecting probes. 60 nm thick Au film was pattered to define Au channel by electron beam lithography followed by lift off process on an oxidized Si substrate. 80 nm thick Py (Ni81Fe19) electrodes with a different aspect ratio (FM1 : 3um X 0.5um, FM2 : 0.2um X Hum) being separated by a distance of 120 ~ 400 nm are fabricated on a pre-patterned Au channel. The nonlocal measurements were carried out at different voltage probe configurations by the standard ac lock-in techniques at 15 K with an excitation current value of 1 mA.