The magneto-optical behaviors modulated by unaggregated system for γ-Fe2O3–ZnFe2O4 binary ferrofluids

Abstract

Under an external magnetic field, when circularly polarized light was transmitted through binary ferrofluids based on strongly magnetic γ-Fe2O3 and weakly magnetic ZnFe2O4 nanoparticles, the birefringence Δn and dichroism Δk arising from the chains of γ-Fe2O3 particles system were modulated and decreased by the unchained ZnFe2O4 particles. In our experiments, we used two types of ZnFe2O4 nanoparticles: one consisted of ZnFe2O4(1) particles with higher moments, and the other consisted of ZnFe2O4(2) particles with lower moments. Comparing the birefringence and dichroism of the γ-Fe2O3–ZnFe2O4(1) and γ-Fe2O3–ZnFe2O4(2) binary ferrofluids, it was found that the modulating action of the ZnFe2O4(2) particle system with lower moments was larger than that of the ZnFe2O4(1) particle system with higher moments. Using a model for a bi-dispersed system based on chained and unchained particles, the behavior of the modulating action was explained by an additional effective relative magnetic permeability, which depends on the background of the unchained ZnFe2O4 particles for the chained γ-Fe2O3 particles and a field-induced demixing phase transition. These results showed that for binary ferrofluids based on both strong and weak magnetic nanoparticles, the power of the modulation of the magneto-optical effects depends on the difference in magnetization between the particles

Modification using additional NaOH for the preparation of γ‐Fe 2 O 3 nanoparticles by chemically induced transition

“…The precursor was synthesised by co‐precipitation, and the nanoparticles were subsequently prepared by chemically induced transition [9, 10]. Such nanoparticles have been applied as ferrofluids [11], nanoparticle mimetic enzymes [12] and nanoparticle films [13].…”

Tunable flat band slow light in reconfigurable photonic crystal waveguides based on magnetic fluids

“…Recently, magnetic fluids (MFs) as plain colloidal materials in magnetics get renewed and extensive interests in optics with the increasing development of optical communications, optical sensing and nanoscience and technology [30][31][32][33][34][35][36][37][38][39]. We have proposed to achieve the extremely large bandwidth and ultralow-dispersion slow light in PC waveguides with MFs as the background [40].…”

Bad neighbour, good neighbour: how magnetic dipole interactions between soft and hard ferrimagnetic nanoparticles affect macroscopic magnetic properties in ferrofluids

“…9 Nanoparticles can even self-assemble spontaneously into chains and rings at zero applied magnetic field when the dipole-dipole energy exceeds thermal fluctuations. 10,11 For ferrofluids, the effect of the modification of the microstructure is very interesting, not only in relation with the magnetic properties (for example, to optimize the efficiency in biomedical applications), but also with the mechanical 12 and optical properties. 13 Several studies have underlined that macroscopic magnetic properties of ferrofluids can significantly be altered by the interparticle magnetic interactions occurring at the nanoscale, [14][15][16][17][18] hence the idea that a fine understanding and tailoring of this nanoscale structuration could allow for a more effective engineering of novel magnetic responsive ferrofluids.…”