An improved technique for the measurement of the complex susceptibility of magnetic colloids in the microwave region

The resonance decay function method in the determination of the pre-factor of the Néel relaxation time of single-domain nanoparticles

“…Measurements of frequency and polarizing field dependence of the complex magnetic susceptibility, χ(ω, H) = χ'(ω, H) -i χ''(ω, H), were made by means of the coaxial transmission line technique [21,22], using a Hewlett Packard (HP) 50Ω coaxial line incorporating a coaxial cell, in conjunction with an HP 8753C network analyzer. The biasing field, H, was varied between 0 and 100 kA/m.…”

Microwave absorbent properties of nanosized cobalt ferrite powders prepared by coprecipitation and subjected to different thermal treatments

“…(2) and (3)) and by the reflection coefficient R. In order to determine these parameters, the frequency dependence of the complex magnetic permeability and of the effective complex dielectric permittivity of the two samples were measured, over the frequency range 0.1 -6 GHz. Measurements were carried out by means of the coaxial line technique [19]. A Hewlett-Packard 50  coaxial line incorporating a coaxial cell with 3 mm inner diameter and 7 mm outer diameter was used in conjunction with a HP 8753C network analyzer.…”

“…Using the complex components of the load impedance, the complex permeability and complex permittivity are determined as detailed in Ref. [19]. The results are given in figures 4 and 5.…”

Experimental Investigations on the Ferromagnetic Resonance and Absorbing Properties of a Ferrofluid in the Microwave Range

“…µ(f,H) and ε(f,H), of the sample were measured using the short-circuited (SC) or open-circuited (OC) coaxial transmission line technique [5,33], over the frequency range (0.4-7) GHz and at values of H, between 0 to 135 kA/m. For this, we have used a Hewlett Packard (HP) 50 W coaxial line incorporating a coaxial cell, containing the ferrofluid sample, in conjunction with the HP 8753C network analyzer [33]. The coaxial cell was placed between the poles of an electromagnet, the axis of cell being perpendicular to the polarizing magnetic field.…”

“…using an inductive method [31] and it shows a Langevin-type dependence [1]. Based on the magneto-granulometric analysis of Chantrell [32] and the M(H) dependence from Figure 3, we have determined the following parameters for the ferrofluid sample, assuming the particles to be of spherical shape: the saturation magnetization of the ferrofluid, Msat = 22.47 kA/m; the mean magnetic diameter of a particle, dm = 8.03 nm; the particles concentration, n = 12.44·10 22 m −3 and initial susceptibility χin = 1.048. μ(f,H) and ε(f,H), of the sample were measured using the short-circuited (SC) or opencircuited (OC) coaxial transmission line technique [5,33], over the frequency range (0.4-7) GHz and at values of H, between 0 to 135 kA/m. For this, we have used a Hewlett Packard (HP) 50 W coaxial line incorporating a coaxial cell, containing the ferrofluid sample, in conjunction with the HP 8753C network analyzer [33].…”