Magneto-electric response in Pb substituted M-type barium-hexaferrite

Kumar, Pawan; Gaur, Anurag; Kotnala, R.K.

doi:10.1016/j.ceramint.2016.10.060

Cited by 41 publications

(9 citation statements)

References 21 publications

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“…2). The Fe 3+ cation in the Fe2 -2b position is Spontaneous polarization was previously observed in diamagnetic doped barium hexaferrites [13][14][15][16][17][18][19][20][21], but the mechanism of its appearance remains unclear. The appearance of a nonzero dipole electric moment, due to the distortion of the oxygen environment of the magnetoactive iron cations, can be a consequence of the order-disorder transition, which is undergoing crystal structure.…”

Section: Methodsmentioning

confidence: 99%

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Magnetic and dipole moments in indium doped barium hexaferrites

Trukhanov

Турченко

Труханов

et al. 2018

Journal of Magnetism and Magnetic Materials

117

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Crystal and magnetic structure of the doped BaFe12-xInxO19 samples were refined by the results of investigations using high resolution neutron powder diffraction and vibration sample magnetometry at different temperatures. The refinements were realized in frame of two space groups. The P63/mmc (No 194) centrosymmetric nonpolar and P63mc (No 186) noncentrosymmetric polar space groups were used. The unit cell parameters, ionic coordinates, thermal isotropic factors, occupation positions, bond lengths and bond angles, microstrain values were established. The magnetic and dipole moments were also defined. It is established that the In3+ cations may be located only in the Fe1 -2a and Fe2 -2b crystallographic positions with equal probability for the sample with lowest substitution level x = 0.1. At the x = 1.2 substitution level about half of the In3+ cations occupies the Fe5 -12k positions. For the last sample the remaining half of the In3+ cations is equiprobably located in the Fe1 -2a and Fe2 -2b positions. The spontaneous polarization was established for these compositions at 300 K. It is studied the influence of the type of substitutive cation and structural parameters on the Fe3+(i) -O2--Fe3+(j) (i, j = 1, 2, 3, 4, 5) indirect superexchange interactions with temperature. With substitution level increase the superexchange interactions between the magnetic positions inside and outside the sublattices are broken which leads to a decrease in the value of their magnetic moments.

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Section: Methodsmentioning

confidence: 99%

“…Mechanism for its realization is also important [11][12][13][14]. This question presents both fundamental scientific interest and it is important from a practical point of view [15][16][17][18][19][20][21][22][23][24][25]. Some controversy about ferroelectricity in the M-type hexaferrites exists [26].…”

Section: Introductionmentioning

confidence: 99%

Magnetic and dipole moments in indium doped barium hexaferrites

Trukhanov

Турченко

Труханов

et al. 2018

Journal of Magnetism and Magnetic Materials

117

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“…All this make substituted barium hexaferrites promising for practical applications, such as radio-frequency absorbing coatings, magnetic recording, fabrication of permanent magnets and various components in microwave devices, telecommunication, etc. As a result, electromagnetic properties [19][20][21][22][23][24][25] and growth methods, such as sol-gel [26][27][28][29][30], co-precipitation [31,32] and the standard ceramic method [33,34], of these compounds are now under extensive investigations.…”

Section: Introductionmentioning

confidence: 99%

Influence of chemical substitution on broadband dielectric response of barium-lead M-type hexaferrite

Alyabyeva¹,

Torgashev²,

Жукова³

et al. 2019

New J. Phys.

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We report on the electrodynamic properties of the single crystalline lead-substituted M-type barium hexaferrite, Ba 0.3 Pb 0.7 Fe 12 O 19 , performed in the broad frequency range including radio-frequency, terahertz and sub-terahertz bands, which are particularly important for the development of microelectronic devices. We demonstrate how changing on a molecular level the chemical characteristics (composition, intermolecular interaction, spin-orbital interaction) of lead-substituted M-type hexaferrite influences its radio-frequency and terahertz electrodynamic response. Our results indicate a critical temperature range, 50 K<T<70 K, where significant changes of the electrodynamic response occur that are interpreted as freezing of dynamical oscillations of bi-pyramidal Fe(2b) ions. In the range 5-300 K, the heat capacity shows no sign of any phase transition and is solely determined by electron and phonon contributions. An anomalous electrodynamic response is detected at 1-2 THz that features a rich set of absorption resonances which are associated with electronic transitions within the fine-structured Fe 2+ ground state and are visualized in the spectra due to magnetostriction and electron-phonon interaction. We show that lead substitution of barium in barium hexaferrite, BaFe 12 O 19 , leads to the emergence of a pronounced dielectric and magnetic relaxational dynamics at radio-frequencies and that both dynamics have the same characteristic relaxation times, thus evidencing the bi-relaxor-like nature of Ba 0.3 Pb 0.7 Fe 12 O 19 . We associate the origin of the relaxations as connected with the motion of magnetic domain walls. In order to unveil crucial influence of chemical substitution on electrodynamic characteristics of the compound, we analyze our results on substituted compound in comparison with the data available for pristine barium (BaFe 12 O 19 ) and pristine lead (PbFe 12 O 19 ) hexaferrites. The obtained spectroscopic data on the dielectric properties of Ba 0.3 Pb 0.7 Fe 12 O 19 provide insight into fundamental phenomena responsible for the absorption mechanisms of the compound and demonstrates that chemical ionic substitution is an effective tool to tune the dielectric properties of the whole family of hexaferrites.

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“…The appearance of

ϵ^{'}

could be attributed to grain boundary defects, oxygen vacancies, and space charge polarization . The high values of

\tan δ

at lower frequencies is as a result of grain boundary effects which require high energy for conduction by hopping of electrons between Fe 3+ and Fe 2+ to occur whereas the small values of

\tan δ

are observed at higher frequencies because of the effectiveness of grains at higher frequencies . Figure presents the variation of AC conductivity with frequency for BaFe 12‐2 x Al x Cr x O 19 ( x = 0.0, 0.2, 0.4).…”

Section: Resultsmentioning

confidence: 99%

Structural, Dielectric, and Magneto‐Optical Properties of Al‐Cr Substituted M‐Type Barium Hexaferrite

Trudel

Mohammed

Hafeez

et al. 2019

Physica Status Solidi (a)

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M‐type barium hexaferrite, BaFe12‐2xAlxCrxO19 (x = 0.0, 0.2, 0.4), is prepared using sol–gel auto‐combustion method and calcined at 1000 °C for 7 h. The effects of Al‐Cr substitution on the properties of the barium hexaferrite are investigated through XRD, FTIR, FESEM, UV‐vis‐NIR, VSM, and impedance analyzer. XRD analysis reveals the formation of hexaferrites with single phase and no impurity phase is detected. FTIR spectra show bands at 437 and 590 cm−1 which indicate the possible of hexaferrites. The micrographs of FESEM shows agglomerated grains with hexagonal plate‐like shape while the EDX spectra confirm the composition of the synthesized samples. Dielectric constant decreases abruptly at lower frequencies and an increment in dielectric constant at much higher frequency region is observed. Grain boundaries dominate the AC conductivity at lower frequencies while the grains could be responsible for the observed dispersion at higher frequencies. The values of coercivity for all the samples are found to be greater than 1200 Oe; this makes the prepared samples useful for high‐density perpendicular magnetic recording media.

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Magneto-electric response in Pb substituted M-type barium-hexaferrite

Cited by 41 publications

References 21 publications

Magnetic and dipole moments in indium doped barium hexaferrites

Magnetic and dipole moments in indium doped barium hexaferrites

Influence of chemical substitution on broadband dielectric response of barium-lead M-type hexaferrite

Structural, Dielectric, and Magneto‐Optical Properties of Al‐Cr Substituted M‐Type Barium Hexaferrite

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