Enhancing perpendicular magnetic anisotropy through dead layer reduction utilizing precise control of Mg insertions

AbstractWe report on the electrical transport properties of Nb based Josephson junctions with Pt/Co$$_{68}$$ 68 B$$_{32}$$ 32 /Pt ferromagnetic barriers. The barriers exhibit perpendicular magnetic anisotropy, which has the main advantage for potential applications over magnetisation in-plane systems of not affecting the Fraunhofer response of the junction. In addition, we report that there is no magnetic dead layer at the Pt/Co$$_{68}$$ 68 B$$_{32}$$ 32 interfaces, allowing us to study barriers with ultra-thin Co$$_{68}$$ 68 B$$_{32}$$ 32 . In the junctions, we observe that the magnitude of the critical current oscillates with increasing thickness of the Co$$_{68}$$ 68 B$$_{32}$$ 32 strong ferromagnetic alloy layer. The oscillations are attributed to the ground state phase difference across the junctions being modified from zero to $$\pi $$ π . The multiple oscillations in the thickness range $$0.2~\leqslant ~d_\text {CoB}~\leqslant ~1.4$$ 0.2 ⩽ d CoB ⩽ 1.4 nm suggests that we have access to the first zero-$$\pi $$ π and $$\pi $$ π -zero phase transitions. Our results fuel the development of low-temperature memory devices based on ferromagnetic Josephson junctions.

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The Correlation Between Magnetic Dead Layer and Perpendicular Magnetic Anisotropy in MgO/CoFeB/Ta Top Structure

IEEE Transactions on Magnetics ◽

10.1109/tmag.2018.2876371 ◽

2019 ◽

Vol 55 (2) ◽

pp. 1-5 ◽

Cited By ~ 2

Author(s):

Shin-Huang Shen ◽

Der-Sheng Lee ◽

Chih-Wei Cheng ◽

Wei-Jen Chan ◽

G. Chern

Keyword(s):

Magnetic Anisotropy ◽

Perpendicular Magnetic Anisotropy ◽

Dead Layer

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Characterizations of the Perpendicular Magnetic Anisotropy in Ultrathin Films of Ta-CoFeB-MgO by X-Ray Photoelectron Spectroscopy

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.739.61 ◽

2013 ◽

Vol 739 ◽

pp. 61-65 ◽

Cited By ~ 2

Author(s):

Chih Wei Cheng ◽

H.M. Chen ◽

C.H. Shiue ◽

Y.Y. Lin ◽

Y.Y. Li ◽

...

Keyword(s):

Thin Films ◽

Magnetic Anisotropy ◽

Photoelectron Spectroscopy ◽

High Performance ◽

Random Access ◽

Perpendicular Magnetic Anisotropy ◽

Magnetic Tunnel Junction ◽

Dead Layer ◽

X Ray ◽

Bottom Structures

The high magnetic anisotropy may enhance the thermal stability of the magnetic tunnel junction of CoFeB/MgO/CoFeB, which is a promising candidate for the high performance magnetic random access memory (MRAM). However, the interface stabilized perpendicular magnetic anisotropy (PMA) is not completely understood at this moment. In this study, we fabricated separated top and bottom Ta-CoFeB-MgO thin films and found both structures showed strong PMA after a 300 °C post annealing. However, the top structure has thicker magnetic dead layer and much higher coercivity relative to the bottom structures. The asymmetry between the top and bottom Ta-CoFeB-MgO structures may be attributed to the crystalline structure and interface diffusion. X-ray photoelectron spectroscopy depth profile reveals that the boron diffuses mainly toward to the Ta side at CoFeB-Ta interface in both top and bottom structures. It is mainly Ta that appears at the CoFeB-MgO interface of top structure while it is TaOx that appears at the CoFeB-MgO interface of bottom structure. A detailed discussion about the chemical states at the interface in Ta-CoFeB-MgO thin films will be given.

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Buffer influence on magnetic dead layer, critical current, and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy

Journal of Applied Physics ◽

10.1063/1.4922499 ◽

2015 ◽

Vol 117 (22) ◽

pp. 223908 ◽

Cited By ~ 11

Author(s):

Marek Frankowski ◽

Antoni Żywczak ◽

Maciej Czapkiewicz ◽

Sławomir Ziętek ◽

Jarosław Kanak ◽

...

Keyword(s):

Thermal Stability ◽

Magnetic Anisotropy ◽

Critical Current ◽

Tunnel Junctions ◽

Magnetic Tunnel Junctions ◽

Perpendicular Magnetic Anisotropy ◽

Dead Layer

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TEM Study of Co/Pd and Co/Au Multilayers

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151015 ◽

1993 ◽

Vol 51 ◽

pp. 1036-1037

Author(s):

A.E.M. De Veirman ◽

F.J.G. Hakkens ◽

W.M.J. Coene ◽

F.J.A. den Broeder

Keyword(s):

Magnetic Anisotropy ◽

Ion Beam ◽

Perpendicular Magnetic Anisotropy ◽

Optical Recording ◽

Magnetic Multilayer ◽

Ion Beam Sputtering ◽

Cross Sectional ◽

Transmission Electron ◽

Beam Sputtering ◽

Substrate Temperatures

There is currently great interest in magnetic multilayer (ML) thin films (see e.g.), because they display some interesting magnetic properties. Co/Pd and Co/Au ML systems exhibit perpendicular magnetic anisotropy below certain Co layer thicknesses, which makes them candidates for applications in the field of magneto-optical recording. It has been found that the magnetic anisotropy of a particular system strongly depends on the preparation method (vapour deposition, sputtering, ion beam sputtering) as well as on the substrate, underlayer and deposition temperature. In order to get a better understanding of the correlation between microstructure and properties a thorough cross-sectional transmission electron microscopy (XTEM) study of vapour deposited Co/Pd and Co/Au (111) MLs was undertaken (for more detailed results see ref.).The Co/Pd films (with fixed Pd thickness of 2.2 nm) were deposited on mica substrates at substrate temperatures Ts of 20°C and 200°C, after prior deposition of a 100 nm Pd underlayer at 450°C.

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