Preparation of ferromagnetic tunneling junctions by ion beam sputtering

We prepared ferromagnetic tunneling junctions by ion beam sputtering technique and measured magnetoresistance and I-V characteristics. Insulating barriers with the barrier height of 0.1-0.6eV were formed by exposing a thin Al metal layer to Ar+O2 beam from the assist ion source. The magnetoresistance of 4% was observed in Fe/Al-O/NiFe/FeMn at 77K. Inserting a thin Co layer between the insulating barrier and the NiFe layer improved the magnetoresistance up to 18%.