Experimental Verification of Interactions Between Randomly Distributed Fine Magnetic Particles

Published

October 1, 2003

Author(s)

S Taketomi, Robert D. Shull

Abstract

We experimentally examined whether or not a magnetic fluid (MF) is really superparamagnetic by comparing the initial magnetic susceptibilities of the mother MFs with those of their highly diluted solutions (more than 1000 times diluted) in which the dipole-dipole interaction between the particles was negligible. We used three mother MFs, SA₁, SB₁, and SC₁, and their highly diluted solutions, SA₂, SB₂, and SC₂, respectively. The particles' dispersability was best in SA₁ and poorest in SC₁. From the static field experiment, it was found that the mutual interaction between the particles in SB₁, and SC₁ made clusters of particles with magnetically closed flux circuits even at zero field while no interaction was detected in SA₁. The initial complex magnetic susceptibility, ac, as a functions of temperature, T, under an ac field experiment revealed that the complex susceptibility of both the samples SA₁ and SA₂ showed peaks as a function of T. However, their Χ vs T curves were not similar, leading to the conclusion that the sample SA₁ was not superparamagnetic. Instead, SA^1^ was a magnetic spin-glass induced by the weak interaction between the particle spins. The existence of the spin-glass state was also confirmed by the linear dependence of the ac-susceptibility peak temperature, T_p, with the frequency of the ac field (i.e., the Vogel-Fulcher law).

Citation

Journal of Magnetism and Magnetic Materials

Volume

266

Issue

No. 1-2

Pub Type

Journals

Keywords

dipole-dipole interactions, magnetic fluid (MF), magnetic susceptibility, supermagnetic

Citation

Taketomi, S. and Shull, R. (2003), Experimental Verification of Interactions Between Randomly Distributed Fine Magnetic Particles, Journal of Magnetism and Magnetic Materials (Accessed April 18, 2024)