Large magnetoresistance in tunnel junctions with an iron oxide electrode

Tunnel junctions combining Co and iron oxide electrodes separated by a well known alumina barrier are fabricated. Large tunnel magnetoresistance (MR) effects reaching 43% at 4.2 K and 13% at room temperature are observed, correlated with the existence of a spinel-like structure for the iron oxide layer. A striking feature of these new junctions is the drop of the MR ratio at low temperature and bias, between ±10 mV, which suggests that the MR comes mainly from the activation of tunneling channels through spin polarized levels above and below E_F in the iron oxide electrode.