Abstract
Ferromagnetic tunnel junctions having naturally oxidized Al barriers were fabricated by magnetron sputtering. The junctions were patterned to 0.01 mm2 with metal masks. The tunnel resistance values varied broadly from 0.1 to 3000 ohms according to the oxidization conditions. Junctions with slightly oxidized (<5 hours) Al barriers had low tunnel resistances. Some of these junctions showed extraordinarily large MR ratios (10-80%), others had different tunnel resistances according to the current-flow path. In contrast, junctions with well oxidized (>100 hours) AI barriers exhibited higher tunnel resistances and good stability. The Ni-Fe/Co/Al-AlOx/Co/Ni-Fe/Fe-Mn/Ni-Fe junction showed a spin-valve-like R-H property. The MR ratio was 10% for a 20 Oe magnetic field. The barrier height calculated from the I-V characteristics was 1.4 eV, and the barrier width was 1.5 nm.
