Comparison of microwave absorption properties of SrFe12O19, SrFe12O19/NiFe2O4, and NiFe2O4 particles

Abstract

In this study, ferrimagnetic (SrFe12O19, SrFe12O19/NiFe2O4, and NiFe2O4) nanostructure particles were synthesized by the co-precipitation of chloride salts using the sodium hydroxide solution. The resulting precursors were heat-treated at 1100 °C for 4 h. After cooling in the furnace, the ferrite powders were pressed at 10 bars and then sintered at 1200 °C for 4 h. The saturation magnetization was increased and the coercivity was decreased by sintering (because of morphology changing) and alternating of the ferrite kind. For example, at SrFe12O19, the saturation magnetization was increased from 291 G to 300 G and the coercivity was decreased from 2.8 kOe to 1.8 kOe by sintering. The microwave absorption properties of the nanostructure particles were studied by ferromagnetic resonance and transmit-line theories, as well as Reflection Loss plots. Before sintering, the RL spectra of SrFe12O19 and the composite were below −3 dB, but they reached −6 dB at 11.1 GHz for NiFe2O4. The RL spectra of the samples were increased by sintering due to reduction of porosity and damping factor. The maximum microwave absorption reached −35 dB (at resonance frequency) for the NiFe2O4 state.

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

“…Thus, taking into account that for many materials  is only weakly frequency dependent at high frequencies [340], the reflection loss depends mainly on the magnetic permeability in a complex way. Thus, since µ depends on M S and K, R L is also controlled by these parameters, as shown by theoretical calculations [339,341] (see Fig. 12).…”

Functional Sr0.5Ba0.5Sm0.02Fe11.98O4/x(Ni0.8Zn0.2Fe2O4) Hard–Soft Ferrite Nanocomposites: Structure, Magnetic and Microwave Properties

“…On the other hand, hard ferrites such as BaFe 12 O 19 have a high ferromagnetic resonance frequency (~35 GHz) and a high magnetocrystalline anisotropy, making them suitable for W-band applications [33]. Consequently, combinations of low anisotropic soft ferrite and high anisotropic hard ferrite are largely used as permanent magnets, as well as for different microwave device applications such as functional devices (circulators and inventors) and antennae [34,35]. Radar absorbing materials (RAM) have excellent microwave absorbing properties due to their high range of 8.2-12.4 GHz [36].…”

Multi-layered nano-hollow spheres for efficient electromagnetic wave absorption

“…μ′ values are observed to decrease up to a certain frequency and then maintain an almost constant value for both bare and bilayered NHSs. Dynamic magnetic properties of the ferrimagnets are strongly related to dc magnetic parameters such as magnetic anisotropy and M S , according to the Landau-Lifshitz-Gilbert equation [16,36,37]. μ″ displays characteristic resonance peaks for MnFO and MnFO@SiO 2 at around 6 GHz.…”