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

Abstract

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 Fe60 Co 20 B20 /Mg-B-O/ Ni65 Fe15 B 20 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. © 2009 American Institute of Physics.