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Competition between and CoPt phases in Pt/Co/AlO x semi tunnel junctions
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10.1063/1.4816620
/content/aip/journal/jap/114/5/10.1063/1.4816620
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/5/10.1063/1.4816620

Figures

Image of FIG. 1.
FIG. 1.

x-ray reflectivity data (points) with fittings (solid lines) for Si/SiO/Pt(3 nm)/Co(0.6 nm)/AlO(2 nm) oxidized during , as-deposited or [(a)] and annealed at [(b)], 300 [(c)], and [(d)]). The curves are shifted vertically for the sake of clarity.

Image of FIG. 2.
FIG. 2.

Thermal annealing ( ) dependence of thicknesses for Pt/Co/AlO samples oxidized during for the following layers: AlO [top-left panel (a)], CoO [top-right panel (b)], Al [bottom-left panel (c)], and Co (for ) or CoPt alloy (for ) [bottom-right panel (d)].

Image of FIG. 3.
FIG. 3.

Thermal annealing ( ) dependence of densities (ρ) for Pt/Co/AlO samples oxidized during in the range (15-25-40-55) s for the following layers: AlO (top part) and Al (inset) [top panel (a)], Co or CoPt alloy (top part), and CoO (bottom part) [bottom panel (b)]. Bulk values are added in straight lines.

Image of FIG. 4.
FIG. 4.

Ratios of the thicknesses of AlO, (AlO) [top-left panel (a)] and Co, (Co) [top-right panel (b)], calculated starting from parameters deduced from fittings of Fig. 1 , as a function of both the oxidation time and the annealing temperature for Pt/Co/AlO samples. and are varied in the (15–60) s and (20–450) °C ranges, respectively. The vertical arrow is the oxidation time starting from the Al layer is fully oxidized, whereas a CoO layer appears. Map of the roughness rms σ of AlO, σ(AlO) [bottom-left panel (c)] and Co, σ(Co or CoPt) [bottom-right panel (d)] for such samples, the scale being in nm. The lowest value of (20 °C) corresponds to the as-deposited sample.

Image of FIG. 5.
FIG. 5.

Co-K edge XANES normalized profiles for as-deposited Pt/Co/AlO trilayers and oxidized for different oxidation time . Note the evolutions of typical peaks [A (pre-edge), B (white line), and C] as a function of . Bulk references for Co and CoO are added for comparison. The 60 s is slightly shifted towards positive absorption for clarity of presentation (very close to the 55 s line).

Image of FIG. 6.
FIG. 6.

Normalized white line area (left), corresponding to the normalized peak B appearing in Fig. 5 , and content of CoO deduced from simulations (right) versus for as-deposited Pt/Co/AlO trilayers. Inset: Example of integration of the white line (normalized intensity) for  = 40 s with the values for the energy ( and ) and the minimal XANES normalized intensity ( ) used for calculating the areas.

Image of FIG. 7.
FIG. 7.

Experimental (a) and simulated (b) Co-K edge XANES data for as-deposited Pt/Co/AlO trilayers as a function of the oxidation time . Here, data are fitted with the help of FDMNES code starting from a linear combination of calculated spectra for Co and .

Image of FIG. 8.
FIG. 8.

Experimental (a)–(d) and simulated (e) Co-K edge XANES data for as-deposited Pt/Co/AlO trilayers oxidized during different oxidation times [(a) 15 s; (b) 25 s; (c) 40 s; (d) 55 s], and annealed for different temperatures (300 °C and 450 °C).

Image of FIG. 9.
FIG. 9.

Co-K edge XANES normalized profiles for as-deposited Pt/Co/AlO trilayers, for in-plane and out-of-plane polarization geometries, and oxidized for [(a)] and 40 s [(b)]. Insets: Zoom of the Co-K edges. Note the differences for only , where the Co-oxygen bonds are reinforced for the out-of-plane configuration (see the arrows).

Image of FIG. 10.
FIG. 10.

Co-K edge XANES normalized profiles for annealed Pt/Co/AlO trilayers at  = 300 °C, for in-plane and out-of-plane polarization geometries, and oxidized for  = 15 s [(a)] and 40 s [(b)]. Insets: Zoom above the Co-K edges. Differences appear for : the contribution of Co-oxygen bonds is stronger for the out-of-plane configuration (see the arrows).

Tables

Generic image for table
Table I.

Crossover value (starting from a fully oxidized Al layer is obtained), thickness , and roughness σ for Co, CoPt, and AlO layers as a function of deduced from fits’ parameters coming from adjustments of reflectivity data. CoPt is uniquely obtained for  = 450 °C. Additional results are given for the sample elaborated for  = 40 s and annealed at  = 300 °C.

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/content/aip/journal/jap/114/5/10.1063/1.4816620
2013-08-02
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Competition between CoOx and CoPt phases in Pt/Co/AlOx semi tunnel junctions
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/5/10.1063/1.4816620
10.1063/1.4816620
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