TY - JOUR
T1 - Ferromagnetic resonance analysis of internal effective field of classified grains by switching field for granular perpendicular recording media
AU - Hinata, Shintaro
AU - Saito, Shin
AU - Takahashi, Migaku
N1 - Funding Information:
We would like to thank Mr. Sato from Bruker Japan Corp. for cooperation in reconstruction of the FMR measurement system. This work was partially supported by the Storage Research Consortium (SRC) and the Japan Society for the Promotion of Science (JSPS) (Kakenhi 22·2544).
PY - 2012/4/1
Y1 - 2012/4/1
N2 - 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.
AB - 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.
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U2 - 10.1063/1.3679466
DO - 10.1063/1.3679466
M3 - Article
AN - SCOPUS:84861722643
SN - 0021-8979
VL - 111
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 7
M1 - 07B722
ER -