Experimental Verification of Interactions Between Randomly Distributed Fine Magnetic Particles
S Taketomi, Robert D. Shull
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, Tp, with the frequency of the ac field (i.e., the Vogel-Fulcher law).
Journal of Magnetism and Magnetic Materials
dipole-dipole interactions, magnetic fluid (MF), magnetic susceptibility, supermagnetic
and Shull, R.
Experimental Verification of Interactions Between Randomly Distributed Fine Magnetic Particles, Journal of Magnetism and Magnetic Materials
(Accessed March 4, 2024)