Large Magnetoresistance at Room Temperature in Ferromagnetic Thin Film Tunnel Junctions

Ferromagnetic-insulator-ferromagnetic tunneling has been measured in CoFe /Al₂O₃ /Co or NiFe junctions. At 295, 77, and 4.2 K the fractional change in junction resistance with magnetic field, ΔR/R, is 11.8%, 20%, and 24%, respectively. The value at 4.2 K is consistent with Julliere's model based on the spin polarization of the conduction electrons of the magnetic films. ΔR/R changes little with a small voltage bias, whereas it decreases significantly at higher bias (>0.1 V), in qualitative agreement with Slonczewski's model. These junctions have potential use as low-power field sensors and memory elements.