The temperature dependence of magnetization in ferrofluids

Abstract

Ferrofluid samples were prepared for magnetic characterization prior to use in a ESA experiment on convection currents in microgravity conditions on the International Space Station. The experiment requires a fluid with a highly temperature dependent magnetization at low field over the temperature range of 30–100°C. Ni–Zn ferrites of varying chemical composition were prepared in order to investigate the effect of a change in the Curie temperature on the temperature dependence of magnetization. Ni0.5Zn0.5 was found to be the composition with the largest ΔM of 0.4emu∕g. Magnetite samples were prepared to investigate the effect of high MS and varying particle size on ΔM. Magnetite fluids with particle sizes of 6 and 10nm have ΔM’s of 0.8 and 1.6emu∕g, respectively. Therefore, the dominant effect is high MS and particle size driven by the field dependence of the Langevin function.

Reduced graphene oxide/nickel nanocomposites: facile synthesis, magnetic and catalytic properties

“…[30][31][32][33] With this in mind, RGObased nanocomposites containing magnetic nanoparticles (Fe 3 O 4 , ZnFe 2 O 4 , CoFe 2 O 4 , Co) have recently been reported. 33,[34][35][36][37][38][39] Ni nanoparticles are important magnetic materials and have found applications as catalysts for hydrogenation of nitrobenzene 40 and thermal decomposition of ammonium perchlorate, 41 as well as fillers for magnetic inks 42 or ferrofluids, 43 while the preparation and properties of RGO cation exchanged graphite oxide. 44 However, long experimental time and high-temperature calcination are required during the procedure, and the properties of the as-prepared RGO/Ni nanocomposites are not studied yet.…”

Particle blocking and carrier fluid freezing effects on the magnetic properties of Fe3O4-based ferrofluids

“…2,[4][5][6][7][8][9][10][11][12][13] Particle size distribution, 4,5 concentration, 6,7 and surfactant coating, 8 as well as solvent used in the suspension, 9 all affect the dipole-dipole interaction, which in turn give rise to the unique range of magnetic behavior observed. [10][11][12][13] In particular, the temperature-dependent complex susceptibility ͑ = Ј − iЉ͒ has been noted in earlier experiments to show two characteristic peaks 11 and the zerofield-cooled ͑ZFC͒ magnetization to exhibit spin-glass-like cusp and magnetic anomaly. 13 However, understanding of the physical origin of these features in ferrofluids remained unclear in part due to the complex nature of the system and the fact that either ac susceptibility 11 or dc magnetization 13 alone was studied separately by different groups.…”

Meniscus of a Magnetic Fluid in the Field of a Current-Carrying Wire: Three-Dimensional Numerical Simulations

“…The strength of the magnetisation depends on two contrary dependencies: the increased volume concentration would increase the magnetisation, whereas the increase of the temperature would decrease the magnetisation; which dependency wins over the other is not clear, as measurements of the magnetisation as a function of the temperature, as in [27], did not determine in parallel the volume concentration. A similar behaviour applies to the density: an increase of the density by an increase in the volume concentration stays contrary to a decrease due to a higher temperature.…”