Atomic-scale electron spectroscopic imaging on sputtered magnetic tunnel junctions ͑MTJs͒ with a thin, Ͻ2 nm, MgO layer and B-alloyed electrodes reveals B diffusion into the MgO, resulting in a Mg-B-O tunnel barrier. This ϳ2 nm thick interfacial layer forms due to oxidation of CoFeB during radio frequency sputtering of MgO and subsequent B diffusion into MgO during annealing. We measure a room-temperature tunneling magnetoresistance ͑TMR͒ of ϳ200% in IrMn/CoFeB/Mg-B-O/CoFeB MTJs after annealing, demonstrating that thin Mg-B-O barriers can produce relatively high TMR.

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006