Activation volumes in CoPtCr-SiO2 perpendicular recording media

Y. Inaba, T. Shimatsu, Hiroaki Muraoka, J. D. Dutson, K. O'Grady

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


CoPtCr-SiO2 perpendicular recording media with varying levels of SiO2 were examined by two different methods to determine the activation volume. The first is based on the sweep-rate dependence of the remanence coercivity using Sharrock's equation. The second is based on the measurement of the fluctuation field from time-dependence data, determined using a magneto-optical Kerr effect (MOKE) magnetometer. The values of V act measured at the coercivity for both methods are almost the same, with the fluctuation field and activation volumes increasing with the SiO 2 content. The difference between Vact and the grain volume measured directly from bright-field TEM images decreases as the SiO 2 content increases due to the reduction of intergranular exchange coupling. The experimental results indicate that values of Vact obtained from single- and double-layered media are consistent. It was also found that the coercivity and normalized hysteresis loop slope at coercivity varied with SiO2 content, with the coercivity peaking at 8 at%SiO 2 (nearly 26 vol%SiO2).

Original languageEnglish
Pages (from-to)3130-3132
Number of pages3
JournalIEEE Transactions on Magnetics
Issue number10
Publication statusPublished - 2005 Oct


  • Activation volume
  • CoPtCr-SiO
  • Fluctuation field
  • Magneto-optic Kerr effect (MOKE)
  • Perpendicular recording media
  • Thermal activation

ASJC Scopus subject areas

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


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