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We investigated the influence of Zr[O.sub.2] on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of [Mn.sub.o.68][Zn.sub.o.25][Fe.sub.2.07][O.sub.4] composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350 [degrees]C for 4 h in [N.sub.2]/[O.sub.2] atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with Zr[O.sub.2] concentration, but excessive Zr[O.sub.2] concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the Zr[O.sub.2] concentration is not more than 0.04 wt% and then decrease with further increase of Zr[O.sub.2] concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of Zr[O.sub.2] concentration. Index Terms--Electromagnetic properties, microstructure, MnZn ferrites, Zr[O.sub.2] addition.

This paper reports on preparation of a magnetically anisotropic polycrystalline hexaferrite, [Sr.sub.0.95] [Ca.sub.0.05] [Fe.sub.12] [O.sub.19], whose orientation degree is as high as 100%. The preparation uses standard ceramic techniques, including wet pressing and flowing-oxygen sintering. In this process, [Ca.sup.+2] ions are substituted for [Sr.sup.+2] ions in Sr[Fe.sub.12] [O.sub.19] by adding minimum impurities ([Bi.sub.2][O.sub.3] and MnC[O.sub.3]). Such a hexaferrite has a dielectric loss lower than 2.3 x [10.sup.-3] at 9.5 GHz, which is important for microwave applications and possibly for millimeter-wave applications. The paper describes the variation of specific saturation magnetization [[sigma].sub.s] and magnetic crystal anisotropy field ([H.sub.a]) with temperature (T), and compares the magnetic properties of the sintered hexaferrite with those of the strontium hexaferrite Sr[Fe.sub.12] [O.sub.19]. Index Terms--Dielectric loss, magneto-crystalline anisotropy, orientation degree, specific saturation magnetization.

The structure and magnetic properties of a series of [Fe.sub.3-x][Mg.sub.x][O.sub.4] (0

Mossbauer spectroscopy and crystallographic methods are used for studying [Li.sub.0.5][Fe.sub.2.5][O.sub.4] powders, which are prepared by high thermal decomposition (HTTD) and sol-gel methods. Mossbauer spectrum of the sample prepared by HTTD method has shown superparamagnetic behavior at room temperature, whereas in sol-gel method, Mossbauer spectra have shown ferromagnetic state of six-line having the hyperfine field values.

The extended x-ray-absorption fine structure-infrared (IR) relationship is used for investigating the effect of various [Fe.sup.2+]/[Fe.sup.3+] ratios in initial synthesis conditions on cation distribution for manganese zinc ferrite (MZFO). The change in manganese occupancy is seen in the iron occupancies, which has helped in describing the variation in saturation magnetization.

X-ray diffraction and Mossbauer spectroscopy are used for investigation the hyperfine structures of piezoelectric and ferromagnetic A[Fe[O.sub.3] (A = Ga, Al) samples prepared by various annealing conditions. The Neel temperature range is decreased with decreasing Fe-O-Fe bond angles between GaFe[O.sub.3] and AlFe[O.sub.3] and the external field dependence of magnetic moment curve is explained by an effect of Fe ion distribution in hyperfine structure.

X-ray diffraction, vibrating sample magnetometer and Mossbauer spectroscopy are used for studying the crystallographic and magnetic properties of [Tb.sub.3-x][Bi.sub.x][Fe.sub.5][O.sub.12] (x = 0.5, 0.75, 1.0 and 1.25). The saturation magnetization at room temperature has increased linearly with increase of bismuth concentration, which is due to the strong exchange interaction between a and d sublattices with increase of bismuth concentration.

The electrical and magnetic tunabilities of high quality bilayer films of Ba[Fe.sub.12][O.sub.19] (BaM)/[Ba.sub.0.5][Sr.sub.0.5]Ti[O.sub.3] (BST), which is grown on a A-oriented sapphire substrates by using pulsed laser deposition (PLD), are examined. Magnetic hysteresis loops have indicated that large magnetic anisotropy between the in-plane and out-of-plane field orientations and the M-H characteristics of BaM are affected by the presence of the BST layer.

Synchrotron x-ray scattering, field emission scanning electron microscope, and vibrating sample magnetometer are used for examining the inhibition of abnormal acicular grain growth of the Ba-ferrite phase in the crystallization of Ba-ferrite films. The Ba-ferrite phase first nucleated at a higher temperature of 750 degree C in comparison to the alpha-Fe2O3 phase, which nucleated at 700 degree Celsius?

Several studies are conducted to explain the application of the domain structures of the garnete-ferrite films for the transportation of magnetic microparticles. This new device is shown to be extremely beneficial for different microbiology, medicine and genetic applications.

Bismuth ferrite nanodics are prepared within Na-4 mica nanochannels, where the nanocomposite has shown weakly ferromagnetic behavior. The dielectric response of the nanocomposite systems is analyzed in very high frequency range at room temperature and this data has shown the presence of resonance interaction.

The article explains the synthesis and properties of the different spinel ferrite composites with flaky fillers that are commonly used as the electromagnetic composites. These composites are shown to be extremely useful as the electromagnetic attenuation materials with various different ultrabroad bandwidths.

The article presents a new approach, which employs the pulsed laser deposition technique for the growth of various different epitaxial spinel ferrite films. The different growth modes exhibited by the films with different shapes at different temperatures are also analyzed.

The effects of a demagnetizing field and an external static magnetic field on the effective SnoekEs product of textured Z-type hexagonal ferrite are examined in order to apply the Z-type hexagonal ferrite to high-frequency devices. The Landau-Lifshitz equation has shown that a large SnoekEs product of over 50 GHz is obtained with an external static field as small as 31 kA/m, which is sufficient to saturate the Z-type hexagonal ferrite.

Several studies are conducted to explain the various magnetic properties and the structural transformation taking place in the nanostructured nickel ferrite compounds. A transformation from the inverse spinel structure to mixed spinel is shown to lead to determine the properties of the compounds.

Several first-principles calculations are conducted to explain the structure, as well as the magnetic properties of the copper ferrite compounds. The electronic structure of the compounds is shown to be completely determined by the distribution of the Cu ions.

The article discusses a new model, which is employed to explain the voltage and current waveforms with saturation and power losses taking place in a ferrite core. The two-dimensional finite elements are used to determine the parameters of the mode, like nonlinear inductance.

The article explains the synthesis, as well as the magnetic and dielectric properties of the various MgTi[O.sub.3] doped [Ba.sub.3][Co.sub.2][Fe.sub.24][O.sub.41] hexaferrites. An increase in the doping is shown to lead to a significant enhancement in the frequency characteristics of permeability of the compounds.

The GalerkinEs method is employed to explain the various dispersion characteristics of the microstrip lines present on the magnetically anisotropic substrates. The wave propagation of the Y- and Z-type hexaferrites is shown to be widely applicable in numerous commercial high frequency applications.

The article discusses a new pulse laser deposition technique, which can be employed for the fabrication of the highly textured manganese zinc ferrite films on glass substrates. The growth of the textured structure is shown to lead to the introduction of stain in these films.

The transmission, as well as the reflection techniques are employed to explain the magnetic permeability, as well as permittivity of the various metal strips coated ferrite disks. A modified measurement technique for determining the traditional transmission-reflection of these strips is also presented.

A new model was developed to detect magnetoelectric (ME) effects in the region of electromechanical resonance (EMR) for ferrite-piezoelectric nanobilayers, nanopillars, and nanowires on a substrate or a template. The application of the model to nickel ferrite-lead zirconate titanate nanostructures on strontium titanate substrate or template revealed that the ME coupling strength decreases with increasing substrate or template volume fraction.

The article describes the various effects of thermal annealing on the structural as well as the high-frequency magnetic properties of the Zn ferrite films that are shown to be deposited by the magnetron sputtering process. Annealing is shown to lead to a significant increase in the saturation magnetization of the films.

A study about the index of refraction of the ferromagnetic metamaterial which is composed of periodic layered ferrite and semiconductor or metallic mesh is reported. The tunable range of the negative index is influenced by the permeability and permittivity of the ferrite and other component materials, as well as their thickness ratios and the ferrite-mesh structure is shown to have a much lower loss than that of a ferrite-semiconductor structure.

Magnetization and Mossbauer spectroscopy measurements are carried out at low temperature under high field, on nanoparticles with a nickel ferrite core and a maghemite shell. The weak surface pinning condition of the nanoparticles has shown that the spin disorder is localized in the external shell and the decrease in underfield in the mean canting angle in the superficial shell is directly related to the unidirectional exchange anisotropy via the interface between the ordered core and the disordered shell.

A laminated-type magnetic wood using ferrite powder and stainless steel powder has served as a wood building material of suitable quality for an indoor electromagnetic wave absorber. The results for the gigahertz frequency band has shown that the laminated-type magnetic wood has an electromagnetic wave absorption characteristic and is used for preventing radio interference for indoor wireless LANs.

Cobalt ferrite nanoparticles are suspended in the polymer liquid crystal hydroxypropyl cellulose (HPC)/m-cresol to obtain a new type of ferronematic. Magnetic measurements performed on HPC/m-cresol/cobalt ferrite ferronematic have indicated the appearance of ferromagnetic behavior and magnetic hysteresis and rheometry has showed magnetorheological effect upon application of a dc magnetic field.

Particle size distributions in manganese ferrite ferrofluids are analyzed based on ac susceptibility measurements. The sample has displayed frequency response due to Neel's rotational relaxation, from which the particle size is estimated.

The time varying biodistribution of ferrite ([Fe.sub.3][O.sub.4]) nanoparticles upon in vivo injection is studied and a novel process of directly labeling radioactive Tc-99m with ferrite nanoparticles is developed. The studies have shown that the particle uptake by organs is very fast and completed within the first few minutes after intravenous injection and the pharmacokinetic behavior of the radiobead uptake is described by a two-compartment model.

The air-core designs of Ethernet transformers in which the reduction of winding magnetic coupling is compensated by increasing the cross-winding capacitance coupling are described. The studies have shown that the capacitive cross-winding coupling has resulted in desirable characteristics of air-core transformers that are similar to those of ferrite core Ethernet transformers.

The performance of tunable notch filters and phase shifters that use BaM hexagonal ferrites as the active element in a small planar device is studied. The notch filter results have shown attenuation of frequencies in the 40-60 GHz range and the phase shifter results have shown phase shifts of up to 360 degree, with losses below 2 dB/cm.

The effects of hydrostatic pressure on the magnetism, capacitance, and impedance of a manganese zinc ferrite device are examined. The analysis has shown that the pressure effects have resulted from the variation of the interior stress in the ferrite.

An efficient route involving facile thermolysis of mixed metal-oleate complexes to form monodisperse ferrite nanocrystals is described. The approach is found to be extremely beneficial, as it gives nanocrystals with uniform composition.

The magnetic and structural characteristics of ErFe[O.sub.3], TmFe[O.sub.3] and YbFe[O.sub.3] single crystals are analyzed. The measurements have not shown any symmetry-lowering lattice distortions during the reorientation, but they have covered a wide range of material parameters and have shown the generality of the modified mean field theory of the orientation phase transitions in orthoferrites.

The variations in the composition and microstructure of Mn-Zn soft ferrites are directly correlated with spatial variations in electrical resistivity. A simple band structure model has modeled the resistivity fluctuations, thus providing a link between the microstructure and macroscopic physical properties of the ferrite material.

A wide range of bias magnetic fields are used to study the electric field tuning characteristics of hybrid microwave resonators, which are based on ferrite-ferroelectric layered structure, experimentally and theoretically. The analysis show that the order of the two resonators used, namely the ceramic barium strontium titanate and the yttrium iron garnet should be equal to control the electromagnetic coupling according to the modes used, whereas the hybrid-wave excitations can be studied theoretically.

A study is conducted which focuses on the structure and magnetic properties of gamma-type hexagonal ferrite, especially the tunable permeability controlled by the direct current (dc) magnetic field. Magnetic permeability mu' declined nonlinearly with the strengthening of a dc magnetic field generated by the bias current at a fixed test frequency.

The nano particle of Ni (sub 1-x) Zn (sub x) Fe (sub 2) O (sub 4) in the size range of 6-12nm synthesized using chemical precipitation and hydrothermal treatment is described. The role of size of particle and precipitation route for cation distribution in nano particles is highlighted.

Nanocrystalline Mn ferrites and MnZn ferrites are produced from metallic precursors by rf plasma torch synthesis and their structural and magnetic properties are characterized. The results clearly demonstrate the viability of plasma torch synthesis for production of ferrite nanoparticles as did the previous report of Ni ferrite synthesis.