High coercivity in heterogeneous Co-rich CoAg very thin films

Author

Butera, A. ; Klemmer, T.J. ; Minor, K. ; Cho, H.S. ; Barnard, J.A.

Author_Institution

Dept. of Metall. & Mater. Eng., Alabama Univ., Tuscaloosa, AL, USA

Volume

34

Issue

4

fYear

1998

fDate

7/1/1998 12:00:00 AM

Firstpage

1114

Lastpage

1116

Abstract

A study of the microstructural and magnetic properties of phase separated Co-rich CoAg very thin films is presented. In the as-deposited state these films form in a very fine grained metastable alloy and are magnetically soft (H_c<20 Oe) in the thickness (5-50 nm) and Co composition range investigated (Co volume percent >65%). After annealing at 420°C for 30 minutes phase separation and grain growth occur and the coercivity is now thickness dependent with a maximum around 15 nm. The maximum coercivity as a function of composition is expected to occur around a volume concentration of 50% for bulk or thick film granular materials. However, for films thinner than 20 nm we have found a maximum H_c>800 Oe at a Co concentration of 70 vol%. This shift in the percolation threshold may originate in the reduced dimensionality of very thin films. Magnetic force microscopy images show a transition in the magnetic domain structure as a function of film thickness that is consistent with this description and the results obtained by transmission electron microscopy

Keywords

annealing; atomic force microscopy; cobalt alloys; coercive force; crystal microstructure; ferromagnetic materials; grain growth; magnetic thin films; segregation; silver alloys; transmission electron microscopy; 15 nm; 30 min; 420 C; 5 to 50 nm; Co-rich CoAg very thin films; CoAg; annealing; coercivity; grain growth; high coercivity; magnetic domain structure; magnetic force microscopy images; magnetic properties; magnetically soft; microstructural properties; percolation threshold; phase separation; transmission electron microscopy; very fine grained metastable alloy; Cobalt alloys; Coercive force; Magnetic films; Magnetic force microscopy; Magnetic properties; Magnetic separation; Metastasis; Soft magnetic materials; Transistors; Transmission electron microscopy;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/20.706391

Filename

706391