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Superparamagnetic Behavior of Granular Co-C Films Consisting of Nanocrystalline Cobalt Encapsulated in Carbon

Published online by Cambridge University Press:  14 March 2011

Hao Wang ,
S.P. Wong ,
W.Y. Cheung ,
N. Ke ,
M.F. Chiah ,
G.H. Wen  and
X.X. Zhang
Hao Wang
Affiliation:
Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China Institute of Thin Films and Nanomaterials, Department of Mathematics and Physics, Wuyi University, Jiangmen, Guangdong, 529020, China
S.P. Wong
Affiliation:
Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
W.Y. Cheung
Affiliation:
Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
N. Ke
Affiliation:
Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
M.F. Chiah
Affiliation:
Department of Electronic Engineering and Materials Science and Technology Research Center, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
G.H. Wen
Affiliation:
Department of Physics, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
X.X. Zhang
Affiliation:
Department of Physics, Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Abstract

Nanocomposite Co-C thin films of about 15 nm thick were prepared by pulsed filtered vacuum arc deposition. The films were characterized by x-ray photoelectron spectroscopy, non-Rutherford backscattering spectrometry, x-ray diffraction, magnetic force microscopy and magnetic measurements. The as-deposited films were amorphous. After annealing at 350°C for one hour in vacuum (< 10−3 Pa), the films were found to consist of nanocrystalline Co grains encapsulated in carbon. The superparamagnetism of the annealed Co36C64 film was demonstrated by the measurement of DC susceptibility and magnetic hysteresis using a SQUID magnetometer. The superparamagnetic relaxation blocking temperature was marked to be about 12K by the peak of the zero-field-cooled magnetization under a field of 100 Oe. The magnetic properties of these annealed granular Co-C films transform from superparamagnetism to ferromagnetism when the Co concentration increases.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 614: Symposium F – Magnetic Materials, Structures & Processing for Information… , 2000 , F2.7.1
Copyright
Copyright © Materials Research Society 2000

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References

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