The optimum oxidation state of AlO/sub x/ magnetic tunnel junctions

Gillies, M. F.; Oepts, W.; Kuiper, A. E. T.; Coehoorn, R.; Tamminga, Y.; Snijders, J. H. M.; Bik, W. M. Arnold

doi:10.1109/20.801062

Cited by 24 publications

(9 citation statements)

References 5 publications

(4 reference statements)

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“…The determination of oxygen was done using the same technique as described in a previous publication where the O content in Al-O tunnel barriers was investigated. 8 To investigate any decrease in magnetic moment due to the oxidation step involved in manufacturing a NOL multilayers of: ͑1͒ 3 nm Ta/͕2 nm Co 90 Fe 10 /NOL ͑60 s in air͖͒ nϭ6 /2 nm Co 90 Fe 10 /3 nm Ta and ͑2͒ 3 nm Ta/14 nm Co 90 Fe 10 /3 nm Ta were grown. The moment of these samples was measured via superconducting quantum interference device ͑SQUID͒ magnetometry.…”

Section: Methodsmentioning

confidence: 99%

Enhancement of the giant magnetoresistance in spin valves via oxides formed from magnetic layers

Gillies

Kuiper

2000

Journal of Applied Physics

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An enhancement of the giant magnetoresistance effect is investigated in spin valves where oxide layers, which are formed from magnetic layers, are incorporated in the structure. Information about Co-Fe based nanooxide layer ͑NOL͒ is obtained via x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Cross-section transmission electron microscopy is also used to explore the effect of an NOL on the polycrystalline structure of the spin valve.

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Section: Methodsmentioning

confidence: 99%

Enhancement of the giant magnetoresistance in spin valves via oxides formed from magnetic layers

Gillies

Kuiper

2000

Journal of Applied Physics

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“…These samples consist of 20 nm Co/1.5 nm Alϩt ox O 2 /15 nm Co on Si, with t ox varying from 5 to 600 s. Details of these measurements are described elsewhere. 11 Here, we will limit the discussion to the results. In Fig.…”

Section: Compositionmentioning

confidence: 99%

Asymmetric bias voltage dependence of the magnetoresistance of Co/Al2O3/Co magnetic tunnel junctions: Variation with the barrier oxidation time

Oepts¹,

Gillies²,

Coehoorn³

et al. 2001

Journal of Applied Physics

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Recently it has been observed that the magnetoresistance (MR) of plasma oxidized exchange biased Co/Al2O3/Co tunnel junctions can have a strongly asymmetric bias voltage (Vbias) dependence. In this article we report on the dependence of this phenomenon on barrier oxidation time tox. For junctions based on 1.5 nm Al, tox was varied from 20 to 120 s. For tox=20 s, for which the MR is approximately 20% at Vbias=0, and for tox⩾90 s symmetric MR(Vbias) curves are found, with the MR decreasing monotonically with |Vbias|. A strong asymmetric bias voltage dependence was observed for intermediate oxidation times, which correspond to essentially full oxidation of the Al layer, but almost no formation of stoichiometric CoO at the bottom electrode. Samples with tox=60 s show even an asymmetric double peak in MR(Vbias). Due to its strength, it has an important consequence for device applications: for a series of junctions with variable tox the maximum signal voltage (at a fixed current) is not necessarily obtained for junctions which have the largest MR ratio at Vbias=0.

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“…The oxygen content in a NOL can be determined with Rutherford backscattering spectrometry ͑RBS͒ in the same way as we did previously for very thin aluminum oxide tunnel barrier layers. 9 The measured oxygen peak areas in RBS can be quantified, yielding the data in Fig. 2.…”

Section: Buried Nol In the Pinned Layermentioning

confidence: 99%