Modification of magnetic nanocontact structure by a bias-voltage-induced stress and its influence on magnetoresistance effect in TaO _x nano-oxide layer spin valve

A magnetic nanocontact spin valve (NCSV) was fabricated by inserting a TaO _x nano-oxide layer (NOL) as the spacer layer. Currentperpendicular-to-film-plane (CPP) measurements revealed that the SV had a positive magnetoresistance (MR) ratio. When a high bias voltage was applied to the SV, the fine structure of the NOL changed i.e., the resistance and MR ratio of the device changed irreversibly. The change in device characteristics is attributed to a proportional change in the number of nonmagnetoresistive and magnetoresistive conductive channels in the SV upon high bias voltage application. The decrease in MR ratio accompanied the disappearance of the magnetic nanocontact, suggesting that the positive MR effect was partially due to the presence of magnetic nanocontacts.