Ni1-xCox–C Nanogranular Thin Films Prepared by a Co-Sputtering Method: Improvement in Magnetic Properties by Optimizing the Alloy Ratio

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Copyright (c) 2001 The Japan Society of Applied Physics
, , Citation Satoshi Tomita Satoshi Tomita et al 2001 Jpn. J. Appl. Phys. 40 6370 DOI 10.1143/JJAP.40.6370

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1 Graduate School of Science and Technology, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan

2 Department of Electrical and Electronics Engineering, Faculty of Engineering, Kobe University, Rokkodai, Nada, Kobe 657-8501, Japan

Dates

  1. Received 11 May 2001
  2. Accepted 9 August 2001

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Abstract

Nanogranular thin films consisting of Ni1-xCox alloy nanoparticles separated by graphitic matrices are fabricated by a co-sputtering method. The structure and magnetic properties of the films are studied. An improvement in their magnetic properties by optimizing the alloy ratio will be demonstrated. Transmission electron microscopic (TEM) observation shows nanoparticles with a small mean diameter (∼ 7 nm) and narrow size distribution (∼ 20% of mean diameter) at the Co/(Ni+Co) ratio (x) ranging from 0 to 0.83. In this region, the coercivity continuously increases with x and manifests a maximum value of 907 Oe at x=0.83. The increase can be explained in terms of alloy formation. With further increasing x up to x=1, the coercivity decreases. The decrease is caused by the existence of extremely large Co particles, which are revealed by TEM observation.

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10.1143/JJAP.40.6370