TEM observations of magnetic domains and grain boundaries on spin-sprayed ferrite films exhibiting high permeability usable for gigahertz noise suppressors

Hideyuki Yoshikawa, Koichi Kondo, Shigeyoshi Yoshida, Daisuke Shindo, Masanori Abe

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Lorentz TEM observations of magnetic domain wall motion, as well as TEM observations of grain boundaries, were performed on spin-sprayed ferrite films #1 (Ni0.17Zn0.22Fe2.61O4) and #2 (Ni0.19Zn0.20Co0.03Fe2.58O 4), both 0.5 μm in thickness. They exhibit much higher natural resonance frequencies than the bulk ferrite and thus have been applied to gigahertz noise suppressors. Films #1 and #2 exhibit prominent and weak in-plane uniaxial magnetic anisotropy, respectively, which is induced along the liquid flow direction during spin-spraying. Both films have columnar crystallites with 100-200 nm widths aligned perpendicular to the film plane, and the boundaries of the crystallites have no pores or impurity phases. Therefore, the crystallites are magnetically exchange-coupled, which is responsible for the unusually high permeability and high natural resonance frequencies of the films. Under zero bias magnetic field, film #1 exhibits mosaic-shaped magnetic domains, whereas film #2 exhibits magnetic domains elongated along the easy magnetization axis, both several hundred nanometers in width. For both films the domain structure remains unchanged when an in-plane bias DC magnetic field, Hdc, of up to 10 Oe is applied along the hard axis. Under a stronger Hdc, the domain structure prominently changes, and the domain walls disappear when H dc exceeds ∼100 Oe. This confirms our previous finding that the initial permeability is ascribed only to magnetization rotation, with no contribution from domain wall motion

Original languageEnglish
Pages (from-to)445-449
Number of pages5
JournalIEEJ Transactions on Electrical and Electronic Engineering
Volume2
Issue number4
DOIs
Publication statusPublished - 2007 Jul

Keywords

  • Domain wall motion
  • Electron microscopy
  • Lorentz microscopy
  • Magnetic domains
  • Noise suppressors
  • Spin-sprayed ferrite films

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

Fingerprint Dive into the research topics of 'TEM observations of magnetic domains and grain boundaries on spin-sprayed ferrite films exhibiting high permeability usable for gigahertz noise suppressors'. Together they form a unique fingerprint.

Cite this