Interfacial Sensitivity and Zero-Bias Anomalies in Magnetic Tunnel Junctions

Abstract

Large zero-bias resistance anomalies as well as an extremely strong decrease of magnetoresistance were observed in Co/Al 2 O 3 /Co magnetic tunnel junctions with thin Cr interfacial layers. The tunnel magnetoresistance decays exponentially with nominal Cr interlayer thickness with a length scale of $ 0:1 nm. The magnetoresistance decay, as well as some aspects of the zero-bias anomalies, can be understood by considering a strong spin-dependent modification of the density of states at Co/Cr interfaces and existing models for zero-bias anomalies. The effect of the density of states modification is also observed in the transport of the metallic electrodes alone, confirming the key role of the Co/Cr interface. However, several aspects of the zero-bias anomalies cannot be explained at present, suggesting perhaps a novel form of the Kondo resonance.

Single electron spintronics

“…Kondo resonances were suggested to be responsible for the increase of the resistance at low temperature and low bias when introducing thin Cr(<0.4 nm)/Co(<0.6 nm) impurities in one of the electrode-barrier interfaces of MTJs [88]. Later, Lee et al [89] studied the resistance and TMR of MTJs with nanoclusters in the lead-insulator interface, produced by over-oxidizing the alumina layer in Co 84 Fe 16 /Al 2 O 3 /Co 84 Fe 16 tunnel junctions.…”

“…Surprisingly, in tunnel junctions with magnetic nanoclusters in the insulating layer, the Kondo effect can produce an enhancement of the resistance or its reduction depending on the exact location of the clusters within the layer. Kondo resonances were suggested to be responsible for the increase of the resistance at low temperature and low bias when introducing thin Cr(<0.4 nm)/Co(<0.6 nm) impurities in one of the electrode-barrier interfaces of MTJs [88]. Later, Lee et al [89] studied the resistance and TMR of MTJs with nanoclusters in the lead-insulator interface, produced by over-oxidizing the alumina layer in Co 84 Fe 16 /Al 2 O 3 /Co 84 Fe 16 tunnel junctions.…”