Effect of viscosity on harmonic signals from magnetic fluid

Takashi Yoshida, Shi Bai, Aiki Hirokawa, Kazuhiro Tanabe, Keiji Enpuku

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We explored the effect of viscosity on harmonic signals from a magnetic fluid. Using a numerical simulation that accounts for both the Brownian and Néel processes, we clarified how the magnetization mechanism is affected by viscosity. When the excitation field varies much slower than the Brownian relaxation time, magnetization can be described by the Langevin function. On the other hand, for the case when the excitation field varies much faster than the Brownian relaxation time, but much slower than the Néel relaxation time, the easy axes of the magnetic nanoparticles (MNPs) turn to some extent toward the direction of the excitation field in an equilibrium state. This alignment of the easy axes of MNPs caused by the AC field becomes more significant with the increase of the AC field strength. Consequently, the magnetization is different from the Langevin function even though Néel relaxation time is faster than time period of the external frequency. It is necessary to consider these results when we use harmonic signals from a magnetic fluid in a high-viscosity medium.

Original languageEnglish
Pages (from-to)105-110
Number of pages6
JournalJournal of Magnetism and Magnetic Materials
Volume380
DOIs
Publication statusPublished - Apr 15 2015

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Magnetic fluids
Relaxation time
relaxation time
Viscosity
viscosity
harmonics
Magnetization
fluids
magnetization
alternating current
Nanoparticles
excitation
nanoparticles
field strength
alignment
Computer simulation
simulation

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Effect of viscosity on harmonic signals from magnetic fluid. / Yoshida, Takashi; Bai, Shi; Hirokawa, Aiki; Tanabe, Kazuhiro; Enpuku, Keiji.

In: Journal of Magnetism and Magnetic Materials, Vol. 380, 15.04.2015, p. 105-110.

Research output: Contribution to journalArticle

Yoshida, Takashi ; Bai, Shi ; Hirokawa, Aiki ; Tanabe, Kazuhiro ; Enpuku, Keiji. / Effect of viscosity on harmonic signals from magnetic fluid. In: Journal of Magnetism and Magnetic Materials. 2015 ; Vol. 380. pp. 105-110.
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