Determination of the radius of nano-particles in a magnetic fluid by means of a constant frequency measurement technique

Abstract

Measurements and analysis are presented of the incremental magnetic susceptibilities, χ∥(H0) and χ⊥(H0), of magnetic fluids subjected to an external polarizing field, H0. The technique of placing a fluid sample in a cylindrical coil positioned between the poles of a magnet and determining the susceptibility, at a fixed frequency, when the long axis of the sample is (1) parallel (χ∥(H0)) and (2) perpendicular (χ⊥(H0)), to H0, provides a convenient method for the determination of the magnetic moment, and hence the effective particle size, of nano-particles in magnetic fluids. Two magnetic fluids samples consisting of magnetite and cobalt-zinc ferrite particles, respectively, are investigated and the results obtained are found to be in good agreement with those of the manufacturer. As the samples are cylindrical in shape, the demagnetizing field, HD, for both the perpendicular and parallel orientations of the samples, is accounted for in calculating χ∥(H0) and χ⊥(H0).

Magnetic nanoparticles with high specific absorption rate of electromagnetic energy at low field strength for hyperthermia therapy

“…A general treatment of the relaxation in ferrofluids based on a Fokker-Planck equation was given by Brown; 49 Rosensweig 40 used the effective relaxation time (1/s eff ¼ 1/s b þ 1/s n ) to calculate the power dissipation in a magnetic fluid under an AMF. The frequency dependence of relaxation of the MNP system can be determined experimentally by measuring the spectra of the complex susceptibility [50][51][52][53][54][55][56][57][58][59] or frequency dependent magnetic field responses from the MNPs.…”

Preparation and properties of temperature-sensitive magnetic fluid having Co0.5Zn0.5Fe2O4 and Mn0.5Zn0.5Fe2O4 nanoparticles

“…Temperature-sensitive magnetic fluid having different Zn-substituted mixed ferrites (Co 0.3 Zn 0.7 Fe 2 O 4 ) for the study of thermal convection have been reported by Fujita et al [8]. The radius of the nanoparticle in a magnetic fluid containing Co 0.7 Zn 0.3 Fe 2 O 4 in a diester carrier has been reported by Fannin et al [9]. In this paper, we report the preparation technique and properties of transformer oil-based temperature sensitive magnetic fluid having Co 0.…”

Rotational Brownian dynamics simulations of non-interacting magnetized ellipsoidal particles in d.c. and a.c. magnetic fields

“…Brownian relaxation implies mechanical rotation of the particle. Experimental techniques for measuring the frequencydependent complex susceptibility,ŵðOÞ ¼ w 0 ðOÞ À jw 00 ðOÞ, have been used to determine the Brownian relaxation time t B and hence the particle size of magnetic fluids composed of spherical particles [5][6][7]. Due to the capability to modify the physical and chemical properties of the suspending fluid in response to impressed magnetic fields, there exists a great interest of magnetic fluids in novel applications such as bio-sensors [8][9][10].…”