2009/04/28 by Derek A. Stewart, Stewart, Derek A.
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Magnetic Properties of Alloys #Materials Science (cond-mat.mtrl-sci) #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Rare-earth and actinide compounds #Superconductivity in MgB2 and Alloys #cond-mat.mes-hall #cond-mat.mtrl-sci
paper · pdf · doi:10.48550/arxiv.0904.4475
11 pages, 4 figures, submitted
arxiv created 2009/04/28 · openalex publication_date 2009/04/28 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Experimental studies of FeCoB/MgO/FeCoB tunnel junctions indicate that boron diffuses into MgO during rf-sputtering and forms polycrystalline Mg-B-O regions. These tunnel junctions provide high tunneling magnetoresistance values and low RA products. However the crystal structure of the Mg-B-O region remains unknown. Using density functional techniques, I examine three potential Mg(B) oxides including Mg2B2O5 (monoclinic and triclinic) and the orthorhombic mineral Kotoite (Mg3B2O6). Kotoite is the best candidate for formation in magnetic tunnel junctions. The (100) surface of Kotoite has a good lattice match with (001) MgO and could template neighboring FeCo into bcc layers during annealing. Complex band structure analysis of Kotoite shows that the C2v Δ1 band has a much smaller imaginary k component than the C2v Δ4 band. Based on symmetry analysis, the majority spin Δ1 band in FeCo should couple well with the Kotoite Δ1 band, while the minority FeCo Δ5 will couple partially with the Δ4 band. Kotoite provides a new route to high tunneling magnetoresistance based on spin filtering by a lower symmetry oxide region.