ISSN 10637397, Russian Microelectronics, 2011, Vol. 40, No. 8, pp. 574–577. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.G. Kostishin, R.M. Vergazov, V.G. Andreev, S.B. Bibikov, S.V. Podgornaya, A.T. Morchenko, 2010, published in Izvestiya Vysshikh Uchebnykh Zavedenii.
Materialy Elektronnoi Tekhniki, 2010, No. 4, pp. 18–21.
The development of modern superbroadband radio
systems requires the development of new measuring
instruments and the modernization of existing ones, as
well as the solution of new tasks concerning electro
magnetic compatibility problems. These tasks cannot
be solved without the equipment of test benches, as
well as radio systems and facilities, with broadband
radio screening and absorbing materials. Nickel–zinc
ferrites are among such promising radio absorbing
materials, because they intensely absorb electromag
netic waves with frequencies ranging from 100 to
700 MHz. However, the further development of
instruments requires the expansion of the frequency
range of the absorption of electromagnetic radiation
by radioabsorbing materials.
The most important parameter of radioabsorbing
ferrites is the reflection coefficient of electromagnetic
radiation, which is defined as the ratio of the reflected
radiation power to the incident radiation power. This
coefficient depends strongly on the processes of the
absorption of the electromagnetic radiation energy
due to resonance phenomena in a ferrite.
In particular, it is known that the absorption of
radiation in nickel–zinc ferrites at frequencies above
300 MHz is due to the ferromagnetic resonance .
Highfrequency losses in this range are caused by the
precession of the magnetization in the internal field
(anisotropy field) of magnetic material. The frequency
of the natural ferromagnetic resonance is determined
by the crystallographic anisotropy constant
material and depends weakly on the grain size .
At a frequency below 300 MHz, the domain wall
resonance plays an important role . The absorption
of electromagnetic radiation is maximal near the fre
quency of their selfoscillations. The condition of res
onance formation is the rigid attachment of domain
walls at the boundaries of grains, pores, or other
defects, which ensures the opposite shift of their sec
tions with respect to the equilibrium positions. The
frequency of selfoscillations of the domain walls
determined by the effective mass of the domain wall
and the stiffness
, which characterizes the quasielas
tic force acting on a wall in the crystal:
According to Eq. (1), an increase in the mass of the
domain wall makes it possible to reduce the resonance
frequency and thereby expands the absorption fre
quency range of the ferrite. Since the mass of the
domain wall is approximately proportional to the area
of the wall surface
[3, 4], the formation of the
coarsegrain structure should lead to a decrease in the
domain wall’s resonance frequency and the spread of
the grain sizes leads to the broadening of the resonance
curve. Below, we analyze the possibility of forming a
coarsegrain structure with a large spread of the grain
sizes in order to expand the frequency range of the
absorption of electromagnetic radiation.
Effect of the Microstructure on the Properties of RadioAbsorbing
V. G. Kostishin
, R. M. Vergazov
, V. G. Andreev
, S. B. Bibikov
, S. V. Podgornaya
and A. T. Morchenko
National Research University MISiS, Leninskii pr. 4, Moscow, 117936 Russia
Kuznetsk Institute of Information and Management Technologies, Kuznetsk, Penza Region, 442530 Russia
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 117977 Russia
—The main approaches and results concerning an increase in the efficiency of broadband radio
absorbing nickel–zinc ferrites are reported. Requirements to the microstructure that ensure the expansion of
the radioabsorption frequency range to 30–830 MHz have been developed. The effect of dopants on the fre
quency dependence of the absorption of electromagnetic waves has been analyzed. The efficiency of the for
mation of the coarsegrain structure with grain boundary layers having a high dielectric constant has been
confirmed. It has been found that both doping with bismuth oxide and the introduction of a coarsegrain frac
tion of the same composition into a batch before the sintering of the powder enhance the absorbing properties
of the ferrites.
: radioabsorbing ferrite, microstructure, grain boundaries, coarsegrain fraction, wireless measure
ment, anechoic chamber, domain wall resonance.
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