Synthesis and characterization of microwave absorbing material

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

“…( 8) and ( 10) and experimental values of the components ε′(f,H) and ε″(f,H) of (Figure 4) and components μ′(f,H) and μ″(f,H) of (Figure 5), the frequency dependence of the reflection coefficient at the interface air-ferrofluid, R, at different values of magnetic field H, was computed and the results are presented in Figure 9. As can be seen from Figure 9, for the reflection coefficient at the interface air-ferrofluid for normal incidence R(f,H), two regions of interest for applications are distinguished: the first region corresponding to frequencies lower than 0.65 GHz when R(f,H) increases with the increase in the H field and the second region in the domain of ferromagnetic resonance (4.2-5.5 GHz), in which R(f,H) decreases with the increase in H. Knowing the values of R(f,H) at the interface air-ferrofluid for normal incidence (Figure 9) and the attenuation constant α(f,H) at microwaves in ferrofluid sample (Figure 7), based Using Equations ( 8) and (10) and experimental values of the components ε ′ (f,H) and ε ′′ (f,H) of (Figure 4) and components µ ′ (f,H) and µ ′′ (f,H) of (Figure 5), the frequency dependence of the reflection coefficient at the interface air-ferrofluid, R, at different values of magnetic field H, was computed and the results are presented in Figure 9. Using Equations.…”

“…Using Equations. ( 8) and (10) and experimental values of the components ε′(f,H) and ε″(f,H) of (Figure 4) and components μ′(f,H) and μ″(f,H) of (Figure 5), the frequency dependence of the reflection coefficient at the interface air-ferrofluid, R, at different values of magnetic field H, was computed and the results are presented in Figure 9. As can be seen from Figure 9, for the reflection coefficient at the interface air-ferrofluid for normal incidence R(f,H), two regions of interest for applications are distinguished: the first region corresponding to frequencies lower than 0.65 GHz when R(f,H) increases with the increase in the H field and the second region in the domain of ferromagnetic resonance (4.2-5.5 GHz), in which R(f,H) decreases with the increase in H. Knowing the values of R(f,H) at the interface air-ferrofluid for normal incidence (Figure 9) and the attenuation constant α(f,H) at microwaves in ferrofluid sample (Figure 7), based As can be seen from Figure 9, for the reflection coefficient at the interface air-ferrofluid for normal incidence R(f,H), two regions of interest for applications are distinguished: the first region corresponding to frequencies lower than 0.65 GHz when R(f,H) increases with the increase in the H field and the second region in the domain of ferromagnetic resonance (4.2-5.5 GHz), in which R(f,H) decreases with the increase in H. Knowing the values of R(f,H) at the interface air-ferrofluid for normal incidence (Figure 9) and the attenuation constant α(f,H) at microwaves in ferrofluid sample (Figure 7), based on Equation (22) we calculated the overall reflection coefficient R w (f,H) for 3 values of the thickness d of the ferrofluid sample: 2 mm, 5 mm and 10 mm.…”

“…Ferrofluids are colloidal systems of single-domain magnetic nanoparticles, having a distribution of sizes between (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) nm being dispersed in a carrier liquid and coated with a surfactant to prevent their agglomeration [1]. Each particle can be in a state of uniform magnetization with the magnetic moment, m = M S V m , where M S is the spontaneous magnetization of the bulk material from which the particles come, and V m is the magnetic volume of the particle.…”

“…In the ferromagnetic resonance range, knowing these parameters of the nanoparticles in the ferrofluid is very important in some microwave applications [9]. Among the practical applications based on microwaves, we can mention the wireless connection, through radio waves, global positioning system (GPS), radar and mobile telephony, and with the progress made in these applications, the problem of electromagnetic interference appears, thus requiring the finding of materials with electromagnetic absorbing properties [10], which are very necessary in the field of electromagnetic shielding [11]. At the same time, the increased use of electronic devices leads to significant pollution with electromagnetic waves, so that the study of electromagnetic wave absorbers (EMAs) is appropriate [12][13][14].…”

“…The design of potential microwave absorbers based on magnetic nanomaterials presents high reflection losses (R L ), thin thickness and wide bandwidth, which leads to improved efficiency in electromagnetic absorption (EM) [16]. In paper [20], a flexible absorber for microwaves based on a nanocomposite of nickel ferrite in a natural rubber matrix was analyzed, using the complex dielectric permittivity and magnetic permeability measurements in S-band (2-4) GHz and X-band (8)(9)(10)(11)(12) GHz. The reflection loss was estimated using the model of single layer absorber deposited on a perfect conductor.…”