Atomic ordering and coercivity mechanism in FePt and CoPt polycrystalline thin films

Author

Jeong, Sangki ; Hsu, Yu-Nu ; Laughlin, David E. ; McHenry, Michael E.

Author_Institution

Dept. of Mater. Sci. & Eng., Carnegie Mellon Univ., Pittsburgh, PA, USA

Volume

37

Issue

4

fYear

2001

fDate

7/1/2001 12:00:00 AM

Firstpage

1299

Lastpage

1301

Abstract

40 nm thick CoPt and FePt films were prepared on oxidized Si substrates with 10 nm MgO underlayers. The maximum coercivity (H_c) for CoPt films was found to be ~10 kOe after annealing at 700°C for ~20-30 minutes (min). Structural analysis showed a significant amount of FCC phase as well as the ordered L1₀ phase in these films. FePt films showed an abrupt increase of ordered volume fraction and H_c in the initial stage of annealing and predominance of the tetragonal L1₀ phase after 10 min. at 700°C. The maximum H_c reached ~16 kOe after annealing at 700°C for more than 20 minutes. Dark field (DF) images of the annealed CoPt films showed individual grains which exhibited a possibility of several variants or disordered phase with dimensions similar to the exchange correlation length, b_cm. The temperature dependence of H_c seems to indicate a weak pinning mechanism in the highly ordered FePt films. Magnetic force microscopy indicated a complex domain structure consisting of clusters with dimensions of several hundred nanometers

Keywords

annealing; cobalt alloys; coercive force; exchange interactions (electron); iron alloys; magnetic domains; magnetic force microscopy; magnetic thin films; platinum alloys; 700 C; CoPt; CoPt polycrystalline thin film; FCC phase; FePt; FePt polycrystalline thin film; MgO underlayer; Si substrate; annealing; atomic ordering; coercivity; dark field imaging; disordered phase; domain pinning; domain structure; exchange correlation length; magnetic force microscopy; structural analysis; tetragonal L1₀ phase; volume fraction; Annealing; Atomic force microscopy; Coercive force; Magnetic anisotropy; Magnetic devices; Magnetic films; Magnetic force microscopy; Magnetic forces; Perpendicular magnetic anisotropy; Transistors;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.950823

Filename

950823