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arXiv 0904.4475cond-mat.mtrl-scicond-mat.mes-hall
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氧化物层硼导致对称性降低的自旋过滤磁性隧道结

Oxide layer boron leads to reduced symmetry spin filtering magnetic tunnel junctions

Derek A. Stewart

摘要:

对FeCoB/MgO/FeCoB隧道结的实验研究表明,硼在溅射过程中扩散到MgO中,形成多晶Mg-B-O区。这些隧道结提供高隧穿磁阻值和低RA产物。然而,Mg-B-O区域的晶体结构仍然未知。使用密度泛函技术,我研究了三种潜在的镁(B)氧化物,包括Mg $_{2}$ B $_{2}$ O $_{5}$(单斜晶系和三斜晶系)和斜方晶系矿物Kotoite(Mg $_3$ B $_2$ O $_6$)。Kotoite是形成磁性隧道结的最佳候选者。Kotoite的(100)面与(001)MgO具有良好的晶格匹配,并且在退火过程中可以将相邻的FeCo模板化为bcc层。Kotoite的复杂能带结构分析表明,C $_{2v}$ $\tildeΔ_1$带具有比C $_{2v}$ $\tildeΔ_4$带小得多的虚k分量。基于对称性分析,FeCo中的多数自旋$Δ_1$带应与Kotoite $\tildeΔ_1$带良好耦合,而少数FeCo $Δ_5$将与$\tildeΔ_4$带部分耦合。Kotoite提供了一种新的途径,高隧穿磁电阻的基础上自旋过滤的低对称性的氧化物区域。

英文摘要:

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 Mg$_{2}$B$_{2}$O$_{5}$ (monoclinic and triclinic) and the orthorhombic mineral Kotoite (Mg$_3$B$_2$O$_6$). 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 C$_{2v}$ $\tildeΔ_1$ band has a much smaller imaginary k component than the C$_{2v}$ $\tildeΔ_4$ band. Based on symmetry analysis, the majority spin $Δ_1$ band in FeCo should couple well with the Kotoite $\tildeΔ_1$ band, while the minority FeCo $Δ_5$ will couple partially with the $\tildeΔ_4$ band. Kotoite provides a new route to high tunneling magnetoresistance based on spin filtering by a lower symmetry oxide region.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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