Dynamics of Magnetic Fluids in Crossed DC and AC Magnetic Fields

Abstract

In this study, we derived the equations describing the dynamics of a magnetic fluid in crossed magnetic fields (bias and alternating probe fields), considering the field dependence of the relaxation times, interparticle interactions, and demagnetizing field has been derived. For a monodisperse fluid, the dependence of the output signal on the bias field and the probe field frequency was constructed. Experimental studies were conducted in a frequency range up to 80 kHz for two samples of fluids based on magnetite nanoparticles and kerosene. The first sample had a narrow particle size distribution, low-energy magneto dipole interactions, and weak dispersion of dynamic susceptibility. The second sample had a broad particle size distribution, high-energy magneto dipole interactions, and strong dispersion of dynamic susceptibility. In the first case, the bias field led to the appearance of short chains. In the second case, we found quasi-spherical clusters with a characteristic size of 100 nm. The strong dependence of the output signal on the particle size allowed us to use the crossed field method to independently estimate the maximum diameter of the magnetic core of particles.

How chains and rings affect the dynamic magnetic susceptibility of a highly clustered ferrofluid

“…One of the most successful approaches is the dynamical modified mean field theory devised by Ivanov and co-workers [12], and subsequently tested against experimental measurements [13][14][15], and computer simulations [16]. An extension of this approach has been made to treat a combination of static and ac (probing) magnetic fields [17,18]. The basic idea is that the local field experienced by a single particle is a superposition of the applied field(s), and the field due to the magnetization of the rest of the particles.…”

Measurement of the response time of magnetorheological fluids and ferrofluids based on the magnetic susceptibility response

“…The relaxation processes of permanent magnetic dipoles in ferrofluids are usually mapped by measuring the magnetic response to weak alternating fields in the frequency domain (FD) (Fannin et al, 1988; Maldonado-Camargo et al, 2016; Pshenichnikov et al, 2019; Tafur et al, 2012). During these AC susceptometry measurements the in and out-of-phase component of the dynamic susceptibility is determined over a wide frequency range.…”

Efecto de las interacciones magnéticas en la disipación de calor de nanopartículas compuestas PCL/magnetita

“…Por otro lado, los parámetros para obtener estas gráficas fueron: H 0 10 kA/m, f 300 kHz y las propiedades magnéticas de la magnetita Tabla 2.2; considerando un momento magnético promedio µ 2.24 ¢ 10 4 µ B [48]…”