Magnetic, dielectric and microwave absorption properties of rare earth doped Ni–Co and Ni–Co–Zn spinel ferrites

In this article we analyze the electromagnetic properties of rare earth substituted Ni–Co and Ni–Co–Zn cubic ferrites in the microwave band, along with their performance as microwave absorbing materials. Ceramic samples with compositions Ni0.5Co0.5Fe2−xRxO4 and Ni0.25Co0.5Zn0.25Fe2−xRxO4 (R=Y and La...

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Vydané v:Journal of magnetism and magnetic materials Ročník 426; s. 629 - 635
Hlavný autor: Stergiou, Charalampos
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: Amsterdam Elsevier B.V 15.03.2017
Elsevier BV
Predmet:
Anisotropy
Ceramics
Chemical compounds
Dielectric properties
Domain walls
Electromagnetic properties
Electromagnetics
Ferrites
Ferromagnetic resonance
Ferromagnetism
Magnetic materials
Magnetic permeability
Magnetic properties
Magnetic resonance
Magnetization
Microwave absorption
Narrowband
Permeability
Permittivity
Rare earth elements
Solid state
Spinel
Wave attenuation
Zinc
Magnetic materials
Ceramics
Dielectric properties
Magnetic properties
ISSN:0304-8853, 1873-4766
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Shrnutí:In this article we analyze the electromagnetic properties of rare earth substituted Ni–Co and Ni–Co–Zn cubic ferrites in the microwave band, along with their performance as microwave absorbing materials. Ceramic samples with compositions Ni0.5Co0.5Fe2−xRxO4 and Ni0.25Co0.5Zn0.25Fe2−xRxO4 (R=Y and La, x=0, 0.02), fabricated with the solid state reaction method, were characterized with regard to the complex permeability μ*(f) and permittivity ε*(f) up to 20GHz. The rare earth substitutions basically affect the microwave μ*(f) spectra and the dynamic magnetization mechanisms of domain wall motion and magnetization rotation. Key parameters for this effect are the reduced magnetocrystalline anisotropy and the created crystal inhomogeneities. Moreover, permittivity is increased with the Y and La content, due to the enhancement of the dielectric orientation polarization. Regarding the electromagnetic wave attenuation, the prepared ferrites exhibit narrowband return losses (RL) by virtue of the cancellation of multiple reflections, when their thickness equals an odd multiple of quarter-wavelength. Interestingly, the zero-reflection conditions are satisfied in the vicinity of the ferromagnetic resonance. As the rare earth doping shifts this mechanism to lower frequencies, loss peaks with RL>46dB occur at 4.1GHz and 5GHz for Y and La-doped Ni–Co–Zn spinels, whereas peaks with RL>40dB appear at 18GHz and 19GHz for Y and La-doped Ni–Co spinels, respectively. The presented experimental findings underline the potential of cubic ferrites with high Co concentration in the suppression of electromagnetic reflections well above the 1GHz region. •Due to cation distribution, magnetic anisotropy drops in Y and La doped samples.•Microwave permeability spectra shift to lower frequencies with rare earth doping.•Permittivity is increased due to crystal modifications, creating dipoles.•Return losses above 40dB from 4 to 19GHz are attained when thickness equals λ/4.•The multiple reflections cancellation is favoured by high imaginary μ′′.
Bibliografia:ObjectType-Article-1
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content type line 14
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2016.11.001