Magnetoresistance of ferromagnetic tunnel junctions with Al2O3 barriers formed by rf sputter etching in Ar/O2 plasma

Abstract

Co/Al 2 O 3 /Ni 80 Fe 20 tunnel junctions were grown by sputtering at room temperature on glass and Si substrates, the barrier being formed by rf sputter etching of aluminum in a Ar/O2 plasma. The resistance is controlled for a given junction area by adjusting the oxide barrier thickness. Magnetoresistance ratios of 16% at 4.2 K and 6% at room temperature are obtained with good reproducibility over three orders of magnitude of resistance. Effects related to substrate shunting and oxidation of the bottom Co electrode are discussed.