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We have measured the complex permeability and permittivity spectra of [Co.sub.2]Z/epoxy composites for different volume concentrations [V.sub.c] varying from 0.2 to 0.6. The effects of [V.sub.c] on matching and bandwidth properties have been studied. For [V.sub.c] [greater than or equal to] 0.5, there exist two matching points. The first matching, occurring away from the magnetic resonance region, has its origin in the quarter-wavelength matching, while the second matching is related to magnetic resonance. Both matchings are perfect, i.e., reflectivity [absolute value of R] (dB) = -[infinity] can be theoretically achieved. For [V.sub.c] [less than or equal to] < 0.4, only one matching, the first matching, is found. At the matching point, [absolute value of R] (dB) is finite. [absolute value of R] (dB) decreases with decreasing [V.sub.c], due to the decrease in tan [[delta].sub.m] and [member of]'. In addition, with an increase in [V.sub.c], the percentage bandwidth [DELTA][W.sub.p] increases and the corresponding optimum thickness [t.sub.o] decreases. A [Co.sub.2]Z/epoxy composite with [V.sub.c] = 0.6 can achieve [DELTA][W.sub.p] = 90% for reflectivity [absolute value of R] (dB) < -10 dB at a thickness of 0.30 cm. Index Terms--Broad bandwidth characteristic, [Co.sub.2]Z barium ferrite, composite materials, EM materials, matching property, reflection property.

Series of polycrystalline samples of Z[n.sub.2-x] C[u.sub.x] Ba F[e.sub.16] [O.sub.27] were prepared by usual ceramic methods, where (x=0.0, 0.4, 0.6, 0.8, 1.0, 1.4). X-ray analysis were obtained at room temperature using Co[[k.sub.[alpha]] with [lambda] = 1.790[A.sup.0] confirmed the presence of W-type hexaferrite phase structure . Saturation magnetization and hysteresis loops curves measurements at room temperature were studied as a function of C[u.sup.2+] substitution. It can be seen that the C[u.sup.2+] content slightly decreases the saturation magnetization from 25 to 20 (emu[g.sup.-1]), all hysterysis loops are closed which indicates low anisotropy field and low saturation magnetization field. The dc conductivity and thermoelectric power was measured in range from room temperature up to T = 750 K for all samples. The thermoelectric power decreases by increasing C[u.sup.2+] content and the conductivity increases with temperature. The value of the charge carrier concentration increases by increasing temperature and C[u.sup.2+] content . Magnetic properties, Electrical properties, charge carrier concentration X-ray analysis, Hexagonal ferrite, INTRODUCTION Hexaferrite powder with a narrow size distribution are promising materials for industrial applications due to their high coercivities and their moderate saturation magnetization (1), (4). Polycrystalline hexaferrite are very [...]

The electromagnetic (EM) and microwave absorption properties of ([Co.sup.2+]-[Si.sup.4+]) substituted barium hexaferrite compositions and its polymer composites, which are prepared from hexaferrite, polyaniline and carbon powders dispersed in polyurethane matrix, are examined. Sintered ferrite and composite absorbers are used for the suppression of electromagnetic interference and reduction of radar signatures.

The study focuses on transition temperature variations as a function of Ba/Ti ratio and in undoped BaTiO(sub)3 powders with particle size to understand stoichiometric effects on transition behavior when materials are processed under equilibrium conditions, before introducing additional degrees of freedom such a dopants, size effect or applied stress. It is found that all the different defects contribute to the changes of transition temperature and enthalpy of transition.

The influence of complex dopants ([Co.sup.2+]+[Ti.sup.4+]) and ([Bi.sup.3+]+[Ti.sup.4+]) on the fine structure and magnetic properties of M-type barium hexaferrite prepared by hydroxide and carbonate precipitations is investigated. The distribution of cations over five nonequivalent positions of barium hexaferrite with magnetoplumbite structure is discussed.

Ferroelectric films of BaSrTiO3 (BST) are identified as a potential alternative to silicon dioxide in the silicon-based microelectronics industry owing to their very high dielectric constant. The distribution of space charge and polarization in BST ceramics is studied at room temperature with the laser induced pressure pulse method.

A series of quasimultilayers of YBa2Cu3O(sub 7-delta)(YBCO)/Y2O3 were prepared on single-crystal SrTiO3 using pulsed-laser deposition. The structural and flux pinning properties are investigated and a series of sample is explicitly compared with different Y2O3 doping contents.

Raman spectroscopy of the two phases that is Ba(Sub7.5)Al(sub 13)Si(sub29) and Eu(sub 0.27)Ba(sub 7.22)Al(sub 13)Si(Sub 29) and the magnetic properties of the phases are presented. It is found that Raman spectra are consistent with both the phases having minimal guest-host interactions and susceptibility data for Eu(sub 0.27)Ba(sub 7.22)Al(sub 13)Si(Sub 29) imply weak magnetic ordering and indicate a 2+ oxidation state for the Eu ion

The crystal chemistry and magnetic properties of polycrystalline Ba(Sub 3)MRuIrO(sub 9) (M(super 1+) = Li, Na; M(super 2+) = Mg, Ni, Zn; M(super 3+) = Bi, In) are investigated. It is found that there are antiferromagnetic interactions within the phase sharing octahedra that contain a disordered mixure of Ru and Ir on a single crystallographic site.

The crystal chemistry and magnetic properties of mixed ruthenium-iridium triple-perovskite series Ba(sub 3)MRuIrO(sub 9) (M = Y, lanthanides) is described. It is found that Ba(sub 3)Ln(super 3+)RuIrO(sub 9) compounds have less weiss constants, low effective magnetic moments at low temperatures, consistent with antiferromagnetic correlation.

Ferroelectric thin films of BaTiO3 and BaTiO3/SrRuO3 epitaxial heterostructures on different single-crystalline substrates were fabricated by pulsed laser deposition. The BaTiO3 films of 100-400 nm thickness show high structural perfection and c-axis-oriented growth.

The role of carrier electrons on ferromagnetism in a half-metallic double perovskite (DP) Ba2FeMoO6 is investigated by means of a partial substitution of Na(super +) for Ba(super 2+). Together with the reported electron-doping effects by La(super 3+) substitution, the Curie temperature (T(sub C)) in the DP oxides systematically increases with increasing carrier concentration, whereas the saturation moment takes a maximum in the absence of the substitution.