Composition-dependent crystal structure and magnetism in nanocrystalline Co-rich alloy

B. S. Chun, J. U. Cho, S. D. Kim, Y. S. Kim, J. Y. Hwang, S. S. Kim, J. R. Rhee, T. W. Kim, J. P. Hong, M. H. Jung, Y. K. Kim

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We report the magnetism of a ferromagnetic two phase mixture system by investigating the microstructural evolution and relevant property changes as a function of alloy composition in CoFeSiB film. The crystal structure evolved from an amorphous to hcp Co nanocrystal embedded two-phase mixture when Co concentration exceeded the critical amount (∼75 at.%) confirmed through TEM and XRD. Very low coercivity value was observed in the amorphous samples. The soft magnetic properties are due to the fact that the magnetic moments of Co-rich phase are exchange-coupled via the amorphous matrix, as a consequence the magnetic anisotropies are averaged out in the amorphous system. Meanwhile, beyond 75 at.% of Co, an abrupt increase in coercivity was observed in the nanocrys- talline samples where highly anisotropic Co nanocrystals were precipitated. The hard magnetic properties resulted from the magnetic decoupling (breaking of the nanocrystal-amorphous matrix-nanocrystal coupling chain) because the exchange forces are not able to overcome the magnetocrystaline anisotropy. We also found that antiferromagnetic exchange coupling existed at the nanocrystal-amorphous matrix interfaces.

Original languageEnglish
Article number5257358
Pages (from-to)3862-3864
Number of pages3
JournalIEEE Transactions on Magnetics
Volume45
Issue number10
DOIs
Publication statusPublished - 2009 Oct

Keywords

  • Co-alloy
  • Nanocrystalline
  • Negative remanence

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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