Spin-dependent inelastic electron tunneling spectroscopy of magnetic tunnel junctions

We investigated the nature of spin dependent scattering by employing inelastic electron tunneling spectroscopy in magnetic tunnel junctions. In this work we introduced a comparable quantity represented as (d²V/dI ²)/(dV/dI) by simultaneous measurements of the dV/dI and d ²V/dI² curves. In each junction we measured, a zero bias anomaly was observed close to the Fermi energy (±2 mV). Furthermore, a relatively large spin dependent scattering occurred around ±18 mV. These peaks and zero bias anomalies were the primary cause of the drop of the tunneling magnetoresistance (TMR) ratio as the bias voltage was applied. Furthermore, insertion of a normal metal between the insulator and ferromagnetic metal was examined. Silver exhibited a reduction of spin dependent scattering, while excess aluminum induced a large zero bias anomaly.