High Magnetoresistance Ratio and Low Resistance–Area Product in Magnetic Tunnel Junctions with Perpendicularly Magnetized Electrodes

We fabricated perpendicularly magnetized MgO-based magnetic tunnel junctions (p-MgO-MTJs) with a [Co/Pt]n/CoFeB/CoFe bottom electrode layer (free layer) and a CoFe/CoFeB/TbFeCo top electrode layer (reference layer). The insertion of thin CoFeB/CoFe layers at the barrier/electrode interfaces and post-annealing at a relatively low temperature of 225 °C simultaneously yielded high magnetoresistance (MR) ratios of up to 85% at room temperature and a low resistance–area (RA) product of 4.4 Ω µm2. Such a high MR ratio in low-RA p-MgO-MTJs is the key to developing ultrahigh-density spin-transfer-torque magnetoresistive random access memories (MRAMs).