Type Hexaferrites Research Articles

Static and Dynamic Magnetic Properties of Polycrystalline Hexaferrites of the Ba2Ni2-xCuxFe12O22 System

The paper presents the results of a study of the phase composition and the main static magnetic characteristics: saturation magnetization, residual magnetization and coercive force of polycrystalline ferroxplana type hexaferrites of the Ba2Ni2-xCuxFe12O22 (0 ≤ x ≤ 2.0) system. These materials have high magnetic permeability and are promising for use as substrates for magnetic antennas and radar absorbing materials. It is shown that thermograms of the initial permeability can be used to quickly assess the presence of impurity magnetic phases in complex oxide ferrimagnets. The permeability and permittivity spectra of textured and non-textured composite samples with the powder of the Ba2NiCuFe12O22 hexaferrite are measured in the microwave frequency range. The radar absorbing properties of the obtained composites are analyzed. It is shown that magnetic texturing leads to an increase in the operating frequency band of an absorber with RL < −10 dB from 6.1 GHz to 8.2 GHz and a deepening of the loss minimum from −21 dB to −27 dB.

Magnetic and spin-phonon coupling studies of magneto-electric SrFe8Co2Ti2O19 M−type hexaferrite

Structural, magnetic, in-field 57Fe Mössbauer and Raman studies of SrFe8Co2Ti2O19 polycrystalline magneto-electric hexaferrite are reported in this article. From bulk magnetization measurements, a transition is observed at 330 K, which is ascribed to a conical like magnetic transition. The population of spin-up and spin-down sites at tetrahedral and octahedral sites are calculated from in-field 57Fe Mössbauer spectroscopic studies. Furthermore, the observed cation distribution suggests that the Co2+ ions occupy the spin-down 4f2 octahedral site, which is reported to stabilize the conical magnetic structure and is expected to play an important role in the magneto-electric properties. Temperature-dependent Raman spectroscopy studies confirmed the spin-phonon coupling in the prepared sample.

Enhanced Stability of the Multiferroic Phase in Cr-Doped Y -Type Hexaferrite Single Crystals

The material family of $Y$-type hexaferrites is among the most promising candidates for magnetoelectric memory applications. The magnetoelectric properties in this class of magnets are dominated by a multiferroic phase, termed the FE3 phase, where spin-driven polarization can be switched by a magnetic field, and, conversely, a full magnetic moment can be reversed by an electric field. In this study, we discuss the effect of Cr doping on the stability of competing magnetic and multiferroic phases in the $Y$-type hexaferrites ${\mathrm{Ba}\mathrm{Sr}\mathrm{Co}}_{2}{\mathrm{Fe}}_{12\ensuremath{-}x\ensuremath{-}\ensuremath{\delta}}{\mathrm{Al}}_{x}{\mathrm{Cr}}_{\ensuremath{\delta}}{\mathrm{O}}_{22}$ with $x=0.9$ and $\ensuremath{\delta}=0.00$, 0.05, and 0.10. We find that Cr doping increases the stability of the multiferroic FE3 phase; while in the Cr-free compound the alternating longitudinal conical (ALC) and proper screw phases are stabilized as zero-field-cooled magnetic phases, the FE3 phase appears besides the ALC phase as a stable zero-field-cooled phase in the $\ensuremath{\delta}=0.05$ and 0.10 compounds. Moreover, a spin-induced large polarization is observed at and above room temperatures with antisymmetric magnetic field dependence. The magnetoelectric properties, in particular the coupling between polarization and magnetization, are investigated via the measurements in the simultaneous presence of electric and magnetic fields. We find the enhanced stability of the magnetoelectic responses from the multiferroic FE3 phase upon Cr doping, while the coupling between the polarization and magnetization is preserved.

Facile synthesis of Yb3+-Zn2+ substituted M type hexaferrites: Structural, electric and photocatalytic properties under visible light for methylene blue removal

Nanocrystalline M type hexaferrites Ca0.5Pb0.5-xYbxZnyFe12-yO19 (x = 0.00–0.1, y = 0.00–1.00) were synthesized by sol-gel autocombustion method. The effects of Yb-Zn doping on structural, optical and electric nature of Ca-Pb M type hexaferrites were explored. The crystal structure of the hexaferrites revealed magnetoplumbite phase with Yb-Zn varying contents (x, y) from 0.00 to 0.1 and 0.00 to 1.00. While the SEM confirmed the presence of well-developed flake shaped particles with size of 16–17 nm. Increase in the dielectric parameters from12.3 to 344.65 k has been observed by dielectric spectroscopy. The results demonstrate that band gap (2.6–2.5 eV) of CaPbFe12O19 can be tuned by the intervention of Yb and Zn ions to enhance the photocatalytic performance. The photocatalytic degradation of methylene blue (MB) dye with undoped CaPbFe12O19 and doped Ca0.5Pb0.5-xYbxZnyFe12-yO19 M type hexaferrites was performed at pH 07 varying time intervals from 0 to 90 min. The Ca0.5Pb0.5-xYbxZnyFe12-yO19 (x = 0.1, y = 1.00) exhibited enhanced percentage degradation efficiency 96.1 % at visible light irradiation in 90 min at pH 07 following the first order kinetics. On the basis of obtained results, Yb-Zn doped CaPbFe12O19 M type hexaferrites can be proposed as excellent material for dielectric, microwave and photocatalyst for the removal of textile contamination.

Dielectric and temperature dependent magnetic studies of Al3+ substituted Ba0.4La0.1Sr0.5AlxFe12-xO19 hexaferrite for microwave application

The Al3+ substituted polycrystalline Ba0.4La0.1Sr0.5AlxFe12-xO19 (0 ≤ x ≤ 1) hexaferrite sample were prepared by the solid-state method. The structural, morphology, dielectric, and temperature dependent magnetic properties are studied systematically. The XRD and Rietveld refinement analysis revealed that all the samples have magneto plumbite hexaferrite structure with space group P6/mmc. The lattice parameters a and c are decreased from 5.888 Å to 5.874 Å and 23.109 Å to 23.085 Å, respectively. The c/a ratio is found to be between 3.92 and 3.93, which is ideal for M−type hexaferrite. It is observed that all the Raman peaks are shifted along the higher wavenumber with increasing Al3+ substitution. The surface morphology of these samples has uniform grain sizes and is closely packed. Also, all the constituent elements are present in proper composition except barium, which has a little higher atomic percentage than the calculated value. The complex dielectric constant (ε', ε“) decreased with Al3+ insertion (for x = 0: ε' = 3.44 k, ε” = 0.993 k; x = 1: ε' = 0.744 k, ε“ = 0.211 k @ 1 MHz). The hysteresis isotherm curves were analyzed by the law of approach to saturation magnetization in the temperature range of 10 K − 300 K. Further, the saturation magnetization and magnetic anisotropy constant K1(T) are found to be decreased, whereas anisotropy field Ha(T) and coercivity HC(T) are rises with an increase in temperature as well as Al3+ concentration. The Bloch’s spin wave theory is used to analyze temperature dependent saturation magnetization, and all the samples get deviated from Bloch’s T3/2 law as well as modified Kobler’s Bloch law. It might be due to finite size effects, long wavelength excitation, and the introduction of constant energy gap into spin wave spectrum, geometrical asymmetries, and other atomic disorders. Finally, Dyson’s approximation which includes T5/2 terms is perfectly fitted with the experimental data. The analysis makes it possible to predict the curie temperature and visualize the nature of the ferromagnetic coupling with the increasing Al3+ concentrations. Above that, the temperature dependent magnetic anisotropy constant K1(T) is linearly fitted with cubic of temperature dependent saturation magnetization MS(T), which confirmed that all the samples have uniaxial hexagonal crystal symmetry. The combination of magnetic and dielectric responses made the material suitable for permanent magnets and microwave applications.

Tuning of structural and dielectric properties of X type hexaferrite through Co and Zn variation

The x-type hexaferrites have been getting considerable attention owing to their promising application in electronic fields. Though, the growth of nanosized crystal X-type hexagonal ferrites is still a big challenge. Herein, the synthesis of nanosized X-type hexagonal ferrites Ca 2 Co 2−x Zn x Fe 28 O 46 (X = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.0) with high quality is reported using the auto-combustion sol-gel method. The objective of the study was to improve the structural and dielectric properties of X-type hexagonal ferrite which was achieved through variation of concentration of cobalt and zinc. Structural, morphological, and dielectric properties were investigated. X-ray diffraction (XRD) patterns confirmed the single-phase x-type hexagonal structure. The crystal size of all samples was in the range of 22.7–23.8 nm. Other parameters such as d -spacing, lattice parameters, unit cell volume, dislocation density, atomic packing fraction, degree of crystal lattice distortion, number of the unit cells, and volume of particles were also calculated. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of metal oxide bonds with two absorption bands at 574 cm −1 and 424 cm −1 . The morphology of the prepared Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Co and Zn was examined by scanning electron microscopy. Increasing crystallinity and agglomeration were observed with the upsurge in Zn and Co. The dielectric properties of Ca 2 Co 2−x Zn x Fe 28 O 46 with the variation of Zn and Co revealed that these materials might be considered good candidates for modern devices. • Nanosized X-type hexagonal ferrites was synthesized by auto-combustion sol-gel. • Crystal size of all samples was in the range of 22.7–23.8 nm. • Dielectric properties revealed that materials are good candidate for devices.

Effect of mechanical milling on magnetic, dielectric and magneto-electric properties of Z- type (Ba, Sr) hexaferrites

The Z-type hexaferrites Sr3Co2Fe24O41 (SCFO) and Ba3Co2Fe24O41 (BCFO) were prepared via sol-gel method and were ball milled for different duration to study the effects of reduction in particle on the physical properties of these compounds. The phase formation was confirmed by using X-ray diffraction (XRD) whereas Scanning Electron Microscopy (SEM) was employed to analyze the surface morphologies of these samples. Magnetization measurements i.e. (M-H) at room temperature were performed by using Vibrating Sample Magnetometer (VSM) and it is observed that the magnetic coercive field (Hc) has increased with reduction in particle of the samples i.e., with ball milling. Magneto electric effects of (Ba, Sr) Z-type hexaferrites at room temperature were measured indirectly by examining the change in polarization (P-E loop) with and without magnetic field. It is evident from P-E loops of SCFO that magnetic field affects the electric polarization for all ball-milled samples and it is an indication of ME coupling in these samples at room temperature.

Synthesis and structural characterization of zinc substituted calcium W-type hexagonal ferrite

Calcium hexaferrites are a subject of great interest due to their promising applications and narrow particle size distribution. It has good magnetic and electrical properties with very good chemical stability along with thermal stoutness with cost effectivity. From the technological point of view substitution of different types of ions was found to be an effective way of improving and enhancing the quality of material and their magnetic characteristics which can lead to various potential applications. The sample of calcium W- type hexaferrite with substitution of Zinc having composition CaZn2Fe16O27 was synthesized using Sol-Gel auto combustion route of synthesis. The enhancement in the properties of the Calcium W-type ferrite with substitution of divalent Zn2+ is not researched and recorded sufficiently. In this paper, the main cornerstone is on the effects of Zn2+ ionic substitution on the structural characteristics of this hexagonal W-type ferrite. The structural modifications of the sample were studied by using XRD and SEM techniques. XRD shows the crystal has the hexagonal structure with lattice parameters a = 5.843 A0 & c = 32.18 A0 belonging to space group P63/mmc. The surface morphology was studied and particle size was confirmed using Scanning Electron Microscope.

Impact of In3+ cations on structure and electromagnetic state of M−type hexaferrites

The solid solutions of In3+ doped M−type strontium hexaferrites were produced using a conventional solid-state reaction method, and Rietveld analysis of the neutron diffraction patterns was conducted. In3+ cations occupy octahedral (4fVI and 12 k) and tetrahedral (4fIV) positions (SG = P63/mmc (No.194)). The average particle size is 837–650 nm. Curie tempearature (TC) of the compounds monotonically decreased down to ∼ 520 K with increasing x. A frustrated magnetic state was detected from ZFC and FC magnetizations. saturation magnetization (Ms) and effective magnetocrystalline anisotropy coefficient (keff) were determined using the law of approach to saturation. A real permittivity (ε/) maximum of ∼ 3.3 at ∼ 45.5 GHz and an imaginary permittivity (ε//) of ∼ 1.6 at ∼ 42.3 GHz were observed for x = 0.1. A real permeability (μ/) maximum of ∼ 1.5 at ∼ 36.2 GHz was observed for x = 0. A μ// imaginary permeability maximum of ∼ 0.8 at ∼ 38.3 GHz was observed for x = 0.1. The interpretation of the results is based on the type of dielectric polarization and the natural ferromagnetic resonance features.

Structural, magnetic and electric properties of Sr0.95Y0.05Fe12-xZrxO19 (x = 0–2) M−type hexaferrites

The ceramic technique has been utilized to fabricate Sr0.95Y0.05Fe12-xZrxO19 (x = 0–2) samples. Structural and Raman-scattering analyses have revealed that the samples with x = 0 and 0.5 possess the M−type hexagonal-ferrite phase, while the others have the additional Zr-related phase. All samples exhibit the hard-magnetic behavior and the magnetic parameters tend to decrease with increasing Zr-doping content. The study on the electric polarization has indicated that the sample with x = 0 shows the coexistence of paraelectric and weak ferroelectric behaviors, while the other samples (x = 0.5–2) show conductive behaviour with nearly circular loops. The changes in the magnetic and electrical properties mainly related to the co-presence of Fe2+ and Fe3+ ions, as evidenced from analyzing X-ray absorption data.

Control of magnetoelectric coupling in the Co2Y -type hexaferrites

We comprehensively investigated the magnetic, ferroelectric, and ME properties of ${\mathrm{Ba}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{Co}}_{2}{({\mathrm{Fe}}_{1\ensuremath{-}y}{\mathrm{Al}}_{y})}_{12}{\mathrm{O}}_{22}$ single crystals in broad doping ranges of Sr $(1.0\ensuremath{\le}x\ensuremath{\le}1.8)$ and Al $(0.00\ensuremath{\le}y\ensuremath{\le}0.08)$. Most of the investigated compounds exhibit an intriguing coexistence of two apparently competing magnetic phases: a transverse conical (TC) and alternating longitudinal conical (ALC) spin structure. The magnetic properties show that the ${\mathrm{Ba}}_{0.2}{\mathrm{Sr}}_{1.8}{\mathrm{Co}}_{2}{({\mathrm{Fe}}_{0.96}{\mathrm{Al}}_{0.04})}_{12}{\mathrm{O}}_{22}$ crystal has the highest ordering temperature and largest volume fraction of the ALC phase at zero H; further, after the application of an in-plane H, it exhibits a maximized volume fraction of the metastable TC phase, resulting in the highest ME susceptibility and electric polarization at all temperatures below 300 K. Our findings demonstrate that securing the thermal stability of the ALC phase is a crucial prerequisite to achieve optimized ME coupling in ${\mathrm{Co}}_{2}\mathrm{Y}$-type hexaferrites, pointing to a general strategy applicable to other hexaferrites as well.

Effect of nominal Indium substitution on structural, magnetic and microwave properties of Calcium-Barium M−type hexaferrites

A series of Indium doped Calcium-Barium M−type hexaferrite with nominal compositions Ca0.5Ba0.5Fe12-xO19Inx (x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25) was prepared by sol–gel method. The x-ray diffraction (XRD) analysis of the synthesized compositions revealed two phases; M−type hexaferrite phase as a main phase and α-Fe2O3 hematite phase. The gradual increasing trend in lattice parameters was observed on increasing Indium concentration showing incorporation of Indium in M−type hexagonal crystal structure. The grain size of M−type hexagonal phase was calculated using Debye–Scherer formula from non-overlapping peaks and it varied from 20 to 500 nm (0.5 μm). The scanning electron microscopy (SEM) micrographs showed hexagonal platelet-shaped, randomly distributed and agglomerated grains. The high resolution transmission electron microscopy (HRTEM) patterns further confirmed the observations of phases from x-ray diffraction (XRD). The remnant magnetization Mr and saturation magnetization Ms showed humped behaviour with maximum value for x = 0.25. The decrease in coercivity Hc was observed for x = 0.05 but it increased and remained nearly constant on further Indium addition. The effective dielectric constant showed resonance peaks at 4.3 and 8 GHz for all compositions and the effective loss decreases with frequency with maximum loss for x = 0.05, indicating the slight effect of In doping. The effective magnetic permeability showed small values and a resonance peak around 9 GHz, similarly magnetic losses also showed low values and a decreasing trend with frequency, not much noticeable influence of Indium doping was observed. These materials can be used in microwave frequency devices such as phase shifters and permanent magnets.

Enhanced structural and electrical properties of Ca-Ba rare earth substituted m –type hexaferrites

Effect of Indium-Manganese (In-Mn) substitution on the structural electrical and dielectric properties of Ca0.5-x Ba0.5InxMnyFe12-yO19 (x = 0.00–0.10; y= 0.00–1.00) hexaferrites prepared by sol–gel auto combustion method was reported. As-synthesized samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrical and dielectric properties (resistivity and conductivity). The X-ray diffraction analysis confirmed the formation of M-type hexaferrite structure. A slight enhancement was found in the in-plane lattice constant a, while the lattice constant c was suppressed with the increasing concentration of In and Mn. The results of SEM images show that the grain size decreases with increase of In-Mn substitution from 10μm to 1μm. The increased dielectric properties and fine particle sizes are useful for many applications, such as cores of inductors, transformers, isolators and magnetic memory devices.

Study of Structural and Magnetic Properties of Ni Substituted M Type Calcium Hexaferrite

Ni substituted M type calcium hexaferrite with composition CaNixFe12-xO19 (x = 0.5, 1.0, 1.5, 2.0) were synthesized by sol - gel auto combustion method. X-ray diffraction analysis confirms the phase composition of prepared samples and reveals that all the samples belong to M type hexaferrite. The crystallite size was determined by the Debye Scherrer formula and W-H Plot analysis method. Lattice parameters (‘a’ and ‘c’) and lattice volume increases with increase in Ni2+ ion concentration. Morphology of the samples was observed by scanning electron microscopes showing that all the prepared samples were hexagonal structure. The absorption band between 516 cm−1–527 cm−1 and 427 cm−1–462 cm−1 in the FTIR study confirms the formation of hexaferrite. With increasing Ni2+ ion concentration the peak position in FTIR and XRD was shifted toward lower frequency and lower angle. Energy-dispersive X-ray spectroscopy analysis confirms the presence of Fe, Ca, Ni and O in all the samples. Vibrating sample magnetometer was used to measure the magnetic parameters such as saturation magnetization, coercivity and remanent magnetization. Saturation magnetization increases from 8.845 emu/gm to 26.05 emu/gm, while the coercivity increases from 162.88 Oe to 184.67 Oe with increasing Ni2+ ion concentration from 0.5 to 2.0 make substituted hexaferrite material suitable for recording media.[AQ1]

Magnetic anisotropies of La–Co substituted M-type Sr hexaferrites studied by 57Fe Mössbauer spectroscopy with external magnetic fields

Magnetoplumbite-(M)-type hexaferrites are the most widely used base materials of permanent magnets. La–Co substitution in these M-type Sr hexaferrites improves these magnetic anisotropies. By 57Fe Mössbauer spectroscopy using the single-crystalline samples, we have investigated the Fe electronic states in the La–Co substituted M-type Sr hexaferrites, Sr1−xLaxFe12−yCoyO19, as a function of an external magnetic field to discuss the enhancement of these magnetic anisotropies. All observed 57Fe Mössbauer spectra were well analyzed using the five subspectra corresponding to the five crystallographic nonequivalent Fe sites. At one site of these five Fe sites, the 2a Fe site, the extracted hyperfine interaction parameters clearly show the Co substitution and external magnetic field dependences, revealing the increments of the 3d electrons in the Fe ions, which are caused by the substitution of Co2+ ions for Fe3+ ions at the neighbor 4f1 Fe site. This hybridization between the Fe ions and the Co ions induces the non-negligible unquenched orbital momentum in the Fe ions at the 2a Fe site. Our findings represent an enhancement of the magnetic anisotropies in Sr1−xLaxFe12−yCoyO19.

Broadband transverse susceptibility in multiferroic Y-type hexaferrite Ba0.5Sr1.5Zn2Fe12O22

Noncollinear spin systems with magnetically induced ferroelectricity from changes in spiral magnetic ordering have attracted significant interest in recent research due to their remarkable magnetoelectric effects with promising applications. Single phase multiferroics are of great interest for these new multifunctional devices, being Y-type hexaferrites good candidates, and among them the ZnY compounds due to their ordered magnetic behaviour over room temperature. Polycrystalline Y type hexaferrites with composition Ba0.5Sr1.5Zn2Fe2O22 (BSZFO) were sintered in 1050 °C–1250 °C temperature range. Transverse susceptibility measurements carried out on these BSZFO samples in the temperature range 80–350 K with DC fields up to ± 5000 Oe reveal different behaviour depending on the sintering temperature. Sample sintered at 1250 °C is qualitatively different, suggesting a mixed Y and Z phase like CoY hexaferrites. Sintering at lower temperatures produce single phase Y-type, but the transverse susceptibility behaviour of the sample sintered at 1150 °C is shifted at temperatures 15 K higher. Regarding the DC field sweeps the observed behaviour is a peak that shifts to lower values with increasing temperature, and the samples corresponding to single Y phase exhibit several maxima and minima in the 250 K–330 K range at low DC applied field as a result of the magnetic field induced spin transitions in this compound.

Preparation and characterization of Ba4Co2Fe36O60 filled PP composites

Phase pure U type hexaferrites having molecular formula Ba4Co2Fe36O60 is synthesized through solid state route as filler for the fabrication of magneto-dielectric (MD) composite. Being a MD material the U type hexaferrite has a promising future in information and communication sector as a base substrate for electronic circuits. Since they exhibit both electric and magnetic properties, they can contribute effectively to circuit miniaturization and bandwidth enhancement compared to an antenna printed on a dielectric substrate. The filler material is then blended with PP (Poly Propylene) matrix and Magneto dielectric substrates are produced via hot pressing technique. Filler concentration has been varied from 70 to 90 wt. % in PP matrix and ascertained amount of optimum filler fraction for dimensionally stable substrate having acceptable properties. Dielectric and magnetic characterizations have been done using Impedance analyzer. It is found that the density of the composite and the dielectric constant is increasing with the increase in filler loading up to an optimum level and further filler loading reduces the density as well as the dielectric constant due to increased porosity. For optimum filler loading a maximum density of 2.96 g/cm3 is achieved. Relative permeability values are found increasing with filler loading even beyond the optimum filler loading. The optimum loaded poly Propylene/Ba4Co2Fe36O60 composite has an effective dielectric constant of 9.21, loss tangent of 0.083, relative permeability of 3.6 and a magnetic loss of 0.060 at 1MHz. Coefficient of thermal expansion (CTE) of the composite has been investigated using thermo mechanical analyzer. Moisture absorption rate of the optimum filler loaded composite is studied and found to be less than 0.1%. Relatively good dielectric constant, low loss tangent together with better relative permeability make the Ba4Co2Fe36O60 filled PP composites an excellent choice as Microwave substrate.

Room-temperature electric field modulation of magnetization in a helimagnet

Room-temperature electric field control of magnetization is of interest for the potential application of low consumption nonvolatile memory. Here, we report the realization of electric field modulation of magnetization in a single phase multiferroic material Ba0.5Sr1.5Co2Fe11AlO22. In this work, we use static and dynamic measurements to reveal the magnetoelectric coupling between magnetization (M) and polarization (P). At the temperature of 10 K, the first order magnetoelectric (ME) term is dominated and the magnetization linearly changes with the electric field. While at room temperature, the quadratic term become apparent, leading to symmetric butterfly-like P–H and M–E curves. Our study reveals that an alternating longitudinal conical (ALC) phase induced exchange interaction may exist in Y type hexaferrite Ba0.5Sr1.5Co2Fe11AlO22 and contribute to the ME coupling mechanism.

Structural, magnetic and electrical study of rare earth doped Y- type hexaferrites

The sol–gel technique was used to synthesize a series of six samples with nominal composition Sr2Co2Fe12 − 2xMnxPrxO22 (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.1). The XRD analysis revealed a well-defined Y-type hexagonal single phase structure. The characteristics such as crystal size, porosity, bulk density, aspect ratio and X-ray density were also calculated by XRD patterns. The crystal size has a range from 59.6 to 25.5 nm. The lattice constant ‘a’ varies from 5.89 A to 5.96 A and lattice constant c varies from 43.35 A to 43.44 A. The surface morphology was performed by SEM analysis of investigated sample. The DC resistivity was calculated and found in the range of 2.86 × 107(Ω cm) to 7.47 × 107(Ω cm). Both dielectric constant, dielectric loss decreased with applied frequency. The variation of values of dielectric constant and dielectric loss was explained with the help of Maxwell Wagner and Koops phenomenological theory. The magnetic properties such as saturation magnetization, retentivity, coercivity of investigated samples was performed through VSM. Due to high resistivity and low dielectric constant these materials are considered best for high frequency microwaves devices.

Conical magnetic structures in multiferroic SrScxFe12−xO19 hexaferrites derived from powder neutron diffraction

We present a systematic powder neutron diffraction study on Sr-based $M$-type hexaferrites ${\mathrm{SrSc}}_{x}{\mathrm{Fe}}_{12\ensuremath{-}x}{\mathrm{O}}_{19}$ using high-resolution and high-flux instruments. We have derived the magnetic configurations for the compounds with $x=1.4$, 1.6, and 1.8 at room temperature and at 2 K revealing a ferrimagnetic structure and a complex conical magnetic structure, respectively, where the latter is decomposed into the axial ferrimagnetic and the helicoidally modulated component in the hexagonal $a\ensuremath{-}b$ plane. Our temperature- and composition-dependent investigation reveals that doping nonmagnetic Sc into this system reinforces the frustration and pushes the transition between the two ordered phases toward higher temperatures. The continuous opening of the spin cone suggests a smooth transition from an easy-axis toward an easy-plane anisotropy with decreasing temperature, which can be reinforced by increasing Sc content.