Tunneling magnetoresistance oscillation effect in double-barrier magnetic tunnel junctions

In this work, we present the fabrication of the double barrier magnetic tunnel junction (DBMTJ) of Ta (5 nm)/Cu (30 nm)/Ni$_{79}$Fe$_{21}$(10 nm)/Ir$_{22}$Mn$_{78}$(12 nm)/Co$_{75}$Fe$_{25}$(4 nm)/Ru(0.9 nm)/Co$_{75}$Fe$_{25}$ (4 nm) /Al(1 nm)-oxide/Co$_{75}$Fe$_{25}$ (1 nm)/ Ni$_{79}$Fe$_{21}$ (2 nm)/ Co$_{75}$Fe$_{25}$ (1 nm)/Al(1 nm)- oxide/ Co$_{75}$Fe$_{25}$ (4 nm)/Ru(0.9 nm)/Co$_{75}$Fe$_{25}$ (4 nm) / Ir$_{22}$Mn$_{78}$ (12 nm)/ Ni$_{79}$Fe$_{21}$ (10 nm)/Cu(30 nm)/Ta(5 nm) on Si/SiO$_{2}$ wafer using Magnetron Sputtering System. Lithographic technique combined with Ar ion-beam etching was adopted in the micro-fabrication processes. Active area of a patterned elliptic DBMTJ element was 3x6$\pi $ $\mu $m$^{2}$. Thus, TMR ratio of 27{\%} and 42.2{\%}, and resistance-area product RS of around 13.6 and 17.5 k$\Omega \mu $m$^{2}$ at 300 K and 4.2 K were obtained respectively. A tunneling magnetoresistance oscillation phenomenon with respect to the bias voltage was first observed in this experiment. Such an effect can be attributed to either the spin-polarized electron coherent and resonant tunneling or the quantum well states. It may open up the possibility of developing novel spintronic devices such as resonant-tunneling spin transistors, etc.