Fabrication of three terminal devices using double barrier magnetic tunnel junctions

Double barrier magnetic tunnel transistors were prepared and the magnetoresistance (MR) and magnetocurrent effect (MC)were measured. The films were deposited on SiO₂ substrate by sputtering. The structure of the films is SiO-substrate/buffer/IrMn/CoFe(2 nm)/Ru(0.85 nm)/CoFe(2 nm:drain)/Al-O(1.2 nm)/NiFe(5 nm:base)/Al-O(1.2 nm)/CoFe(3 nm:source)/IrMn(1.5 nm)/Ru(5 nm). (Hereafter "drain layer" is denoted as "D", "base layer" is "B" and "source layer" is "S".) Al-O tunnel barriers were formed by plasma oxidation of Al. The films were fabricated into 3 terminal device using photolithography, Ar ion etching for metallic layers and wet etching for Al-O layers. The area of D/B junction is 40×90 μm², and B/S junction area is 10×10 μm². The product of resistance and area (RA) is 1.8 MΩμm² for D/B junction and 0.2 MΩμm for B/S junction, respectively. MR measurements were done by conventional 4-probe method at 10 mV. MC measurements were done by using two Keithley 2400 source meters.