High magnetoresistance tunnel junctions with Mg–B–O barriers and Ni–Fe–B free electrodes

The use of boron-alloyed electrodes with the radio frequency (rf) sputter deposition of MgO yields magnetic tunnel junctions (MTJs) with Mg–B–O tunnel barriers. After annealing, such MTJs can exhibit very high tunneling magnetoresistance (TMR) in the thin (∼1.0 nm) barrier regime. Scanning tunneling spectroscopy of Mg–B–O layers reveals a better defined, but smaller band gap in comparison to that of thin MgO. We produced Fe60Co20B20/Mg–B–O/Ni65Fe15B20 MTJs where after a 350 °C annealing the Ni–Fe–B free electrode crystallizes into a highly textured (001)-normal body centered cubic (bcc) crystal structure and the MTJs achieve 155% TMR.