Hall resistance as a function of the applied field for samples under plasma oxidation for various oxidation times. The field is applied perpendicular to the plane of the trilayers.
EHE with perpendicular field for three characteristic oxidation times: (a) , (b) , and (c) . EHE with planar field (tilted from the layer plane with an angle ) for three characteristic oxidation times: (d) , (e) , and (f) . is the saturation field for which the magnetization lies out of plane in a single domain structure, and is the perpendicular anisotropy field. Inset: schematics of the magnetic configuration of the Co layer submitted to the external field.
Out-of-plane anisotropy field of Pt/Co/AlOx samples measured by EHE as a function of the oxidation time.
XAS spectra of the Pt/Co/AlOx trilayers for (a) underoxidized, (b) optimally oxidized, and (c) overoxidized samples and their corresponding derivatives [(d), (e), and (f)] at edge. Spectra of Co are given in (a) and (d) and spectra of CoO are given in (c) and (f). The solid and dotted vertical lines indicate the energy position of the shoulders in the XAS spectra due to Co and CoO, respectively.
Ratio of oxidized aluminum estimated from x-ray photoelectron spectra. The solid line is a guide for the eyes. Inset: XPS spectra with its Shirley background (solid line) for a sample oxidized for . The dotted lines are the Gaussian fits of the XPS peaks and the dashed line is the sum of these estimated peaks.
XPS spectra for samples for different oxidation times .
Ratio of oxidized cobalt estimated from x-ray photoelectron spectra as a function of the oxidation time. The shaded area indicates the oxidation time and the related ratio of oxidation for which the magnetization lies out of plane.
Initial slope and amplitude of the hysteresis loops measured by EHE for samples under natural oxidation with , Ta, Mg, and Ru. The dotted and solid lines are guides for the eyes.
Schematics of the influence of the oxidation on the magnetic properties of the Co layer in a Pt/Co/AlOx trilayer: (a) for very small oxidation times, the magnetization lies in the plane; (b) for small oxidation times, the magnetization lies out of plane forming domain structure; (c) for optimal oxidation times, the magnetization lies out of plane in a single domain structure; and (d) for long oxidation times, the magnetization lies out of plane forming domain structure.
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