Magnetic tunnel junctions with in situ naturally-oxidized tunnel barrier

Al/Fe/Al2O3/CoFe/Al junctions with dimensions of 2 x 2 - 40 x 40 mu m(2) were prepared on a 2 in. Si wafer using conventional photolithography and ion-beam etching. The junction trilayers were deposited sequentially without breaking vacuum and a tunnel barrier was in situ naturally oxidized. The resultant junction resistance scaled linearly with the junction area over all dimensions used, Normalized resistance of less than 1.5 x 10(-5) Omega cm(2) was obtained in maintaining a magnetoresistance (MR) ratio of about 5%. The resistance values are much smaller than ever reported and close to those required for an MR head device. The MR ratio exhibited no significant change up to at least 1 x 10(3) A/cm(2) with increasing junction current density. (C) 1997 American Institute of Physics.