Low resistance spin-dependent magnetic tunnel junction with high breakdown voltage for current-induced-magnetization-switching devices

Spin-dependent magnetic tunnel junctions (MTJs) with pure Al Ox barriers were fabricated by one-step and two-step natural oxidation processes, respectively (500 mTorr 20 min; 500 mTorr 5 min and 1 Torr 10 min). Preoxidized Al barrier thickness varies from 5 to 7 Å. In this work, a multilayer structure with a low resistance of 0.8 ωsq and rms of 1.54 Å was developed as the bottom electrode. MTJs with the following structure Ta (30 Å) NiFe (40 Å) MnIr (80 Å) CoFe (30 Å) Al+oxidationCoFe (30 Å) NiFe (40 Å) Ta (200 Å) were magnetically annealed at 230 °C for 30 min to set the exchange bias field in the MnIrCoFe bilayer. Resistance×area (RA) products varying from 0.5 to 13 ωμ m2 were achieved with tunneling magnetoresistance ratios varying from 8% to 18%. Breakdown voltages higher than 450 mV were obtained for a sample with RA 0.5 ω×μ m2, which allows a current of 9× 107 A cm2 to flow through the MTJ without damaging the barrier. Current-induced magnetization switching based on spin transfer or spin torque effect with a current density of 1.4× 107 A cm2 for a developed MTJ cell was achieved.