Evidence of a barrier oxidation dependence on the interfacial magnetism in Co/alumina based magnetic tunnel junctions

Abstract

Soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co L 2,3 edge have been applied to explore the near-interfacial magnetism of Co electrodes in Co/alumina based magnetic tunnel junctions. By taking into account the formation of CoO at the ferromagnetic ͑FM͒/barrier interface, the change in the total magnetic moment on metallic Co atoms as a function of barrier oxidation has been determined. The results demonstrate a strong correlation between the Co moments and measured TMR values, and an enhancement in the Co moments for moderate oxidation times.

Competition between CoOx and CoPt phases in Pt/Co/AlOx semi tunnel junctions

“…Besides techniques dedicated to magnetic and transport measurements, 15 those commonly used are cross-sectional high resolution electron microscopy, 16 in situ differential ellipsometry measurements coupled to xray photoelectron spectroscopy (XPS), 17 ac impedance, 18 photoconductance, 19 soft x-ray absorption. 20 All these techniques have some of the following drawbacks: (1) study limited at the top layers, buried layers are not investigated, (2) necessity of high vacuum environment, (3) induced destruction of the sample, (4) difficulty to reach a sub-nanometric resolution for very thin layers (some angstroms), and (5) determination of the thicknesses of the layers but without additional pertinent structural parameters, as the roughness or the film density.…”

X-ray analysis of oxygen-induced perpendicular magnetic anisotropy in trilayers

“…Consequently, one can expect a strong enhancement of PMA due to the presence of Co-O bondings at the interface. X-ray studies achieved by Telling et al [12,13] on Co=AlO x =Co MTJs showed that a maximum of Co magnetic moment, corresponding to a maximum in TMR, can be reached by optimally oxidizing the tunnel barrier. Designing high TMR-MTJ using oxygen-induced PMA [6] requires a deep understanding of this phenomenon.…”

Interface effects in spin-polarized metal/insulator layered structures

“…With regard to increased moment due to interfacial oxidation, there are some [282] who argue that such induced moment is absent based on empirical data. Recently, experimental [267,283,284] and theoretical work [237,285,286] has shown that there is an optimum level of interfacial oxidation where TMR reaches a maximum. Such work has been completed for Co/Al 2 O 3 and Fe/MgO interfaces, where each system provides similar results, despite rather disparate physical ordering, i.e.…”