Effective nonlocal spin injection through low-resistance oxide junctions

• A large number of nonlocal spin valves on the same substrate are fabricated and characterized.
• Oxide barriers with low resistance (<1 Ω) are utilized as spin injection (detection) interfaces.
• Substantial nonlocal spin signals are observed indicating efficient spin injection and detection.
• New methods are proposed to quantify the nonlocal spin signals.

Many (>40) nonlocal spin valves on the same substrate have been characterized at 6 K and 295 K by using a probe station. Low-resistance oxide junctions (0.2–0.8 Ω) are used to inject spin current into mesoscopic Cu channels. Spin signals exceeding 10 mΩ at 6 K have been consistently observed, indicating efficient spin injection and detection. However, complex switching behavior and possible variations between devices pose a challenge to using a standard fitting method to quantify the spin signals. Two methods are used for quantitative analysis. The range of the effective spin polarizations can be estimated by assuming a reasonable range for the Cu spin diffusion lengths. A nonlocal spin polarization is introduced to evaluate the spin current in the Cu channels.