Ferromagnetic resonance analysis of internal effective field of classified grains by switching field for granular perpendicular recording media

Shintaro Hinata, Shin Saito, Migaku Takahashi

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Abstract

The internal effective fields H eff of granular perpendicular magnetic recording media with a switching field (SF) distribution were measured by ferromagnetic resonance (FMR) by sweeping the external field H DC. H eff consists of the anisotropy field H k, the dipole interaction field, the self-demagnetization field, and the intergranular exchange (coupling) field H ex for up and down magnetic moments of magnetic grains classified by their SF. Prior to the measurement, magnetic grains were classified into two classes: Those with high and low SFs when H DC is swept from 18 kOe to a negative field. FMR measurements were performed in a range for which the same domain structure was retained for typical strong and weak intergranular exchange coupled media (media I and II, respectively). These measurements revealed the following points. (1) Resonances originating from majority-direction moments were observed, whereas those of minority-direction moment were not. (2) The increase in H eff with decreasing 4M for medium II is larger than that for medium I. (3) H ex can be expressed as H k - 4πM -H eff when the sum of dipole interaction field and self-demagnetization field is assumed to be the average field 4M. H ex/H k was evaluated to be 0.25 (for grains with low SF) and 0.37 (for grains with high SF) for medium I and 0.09 (for both low and high SF) for medium II under M 0.

Original languageEnglish
Article number07B722
JournalJournal of Applied Physics
Volume111
Issue number7
DOIs
Publication statusPublished - 2012 Apr 1

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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