Interfacial microstructure of Fe∕AlO[sub x]∕Fe magnetic tunnel junctions in high resolution

Magnetic tunnel junctions were prepared by deposition of a Ta-buffered Fe-AlOx-Fe trilayer on a thermally oxidized silicon wafer. In order to investigate the influence of different Fe oxides like a spinel-like phase and a spinel (Hycernite) on the tunneling magnetoresistance effect, a 57Fe tracer was deposited at the lower barrier interface. Using conversion electron Mössbauer spectroscopy the evolution of chemical, structural, and magnetic changes in the tracer was monitored starting from the as-prepared state and after several annealing steps. The nuclear probe technique enables to resolve phase formation at the interface with submonolayer resolution