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Z-type barium hexaferrite particles were synthesized by a one-step mixing-calcination process (MCP) and its magnetic properties were characterized and compared to the sol-gel (SGP) and the conventional ceramic (CCP) processed Z-type Ba hexaferrite with two-step calcination. We have used 71.2 % pure M-type (Ba[Fe.sub.l2][O.sub.19]) and 83.8% pure Y-type ([Ba.sub.2][Co.sub.2][Fe.sub.12][O.sub.22]) precursors to synthesize Z-type by the MCP. As a result, 77.8 % pure [Co.sub.2]Z hexaferrite particles were obtained. The purities of [Co.sub.2]Z hexaferrite particles processed by SGP and CCP were 75.1% and 70.7%, respectively. It was found that purity of Z-phase was controllable by purity of M- and Y-type precursor particles in the MCP. Loss tan [delta] of sintered MCP [Co.sub.2]Z decreased from 0.17 at 50 MHz to 0.068 at 300 MHz, while loss tan [delta] of sintered SGP and CCP [Co.sub.2]Z were 0.12 and 0.09 at 300 MHz. It is found that this loss tan [delta] is controllable by the purity of Z-phase and sintering process. These results imply that our new process is potentially applicable to synthesis of any other hexaferrites and also cost-effective. Index Terms--Barium ferrite, [Co.sub.2]Z, hexaferrite, Z-type.

The influence of the speed of the switching process on the nonequilibrium domain structures in magnetic thin-film elements undergoing large angle rotations was studied with time-resolved scanning Kerr microscopy and numerical modelings. In particular, the systematic evolution of the spatiotemporal nature of the reversal of a small [Ni.sub.80][Fe.sub.20] element to progressively faster switching fields has been investigated. Generally, the magnetization evolves into a complex domain structure in nonequilibrium state when a magnetic element is excited by applying a short magnetic field pulse. The degree of complexity of the nonequilibrium domain structure is found to be a strong function of the speed of the switching process. Index Terms--Magnetic domains, magnetization reversal, magnetooptic Kerr effect, simulation.

The switching dynamics of the magnetic vortex core in a submicrometer-scale Permalloy disk is investigated by micromagnetic modeling. At zero magnetic field, the vortex state is formed with a single vortex core at the disk center. When an in-plane magnetic field pulse with an appropriate strength and duration is applied to the vortex structure, an additional two vortices, i.e., a vortex and an anti-vortex, with an opposite polarity are created near the original vortex core. Subsequently, the original vortex core annihilates with the antivortex core, and the final magnetic state contains a single core with the reversed polarity. The dynamics of the vortex core switching are discussed in terms of the nonlocal torque exerted to spins in response to an externally applied magnetic field pulse. Index Terms--Magnetic domains, magnetization processes, magnetization reversal, simulation.

Nonequilibrium magnetization configuration and magnetic switching behavior are studied using micromagnetic modeling. In particular, it is found that coherent rotation and magnetization ringing in submicrometer [Ni.sub.80][Fe.sub.20] elements can be controlled by adjusting the axis-ratio of the ellipse, the thickness, and the angle of the magnetic field pulse with respect to the axis of elliptical elements. For the element with 400-nm-long axis, 200-nm-short axis, and 4.7-nm thickness, the nonuniform distribution of magnetization results from a strong in-plane, nonuniform demagnetization field during magnetization precession. The simulation results indicate that uniformity in the distribution of the magnetization during reversal is improved by reducing the length of the short axis from 200 nm to 112 nm, and reducing the thickness of the thin film from 4.7 to 3.2 nm. The modification in the geometric configuration of the element is found to effectively suppress the magnetization ringing. Index Terms--Magnetic domains, magnetization dynamics, magnetization reversal, micromagnetic modeling.

A combination of energetic shake-milling and a subsequent double sintering process was employed to synthesize [Co.sub.0.8][Zn.sub.l.2]Z([Ba.sub.3] [Co.sub.0.8 [Zn.sub.1.2] [Fe.sub.24][O.sub.41]) hexaferrite nanoparticles with a high-saturation magnetization and a low coercivity. A homogeneous mixture of Ba.C[O.sub.3], CoO, ZnO, 40-nm sized [alpha]-[Fe.sub.2][O.sub.3], and heat-treating in an oxygen environment were important factors for synthesizing single-phase [Co.sub.2]Z-type ferrite nanoparticles. In addition to an X-ray diffraction pattern, Miissbauer spectra confirmed that only [Fe.sup.3+] cations are present in the synthesized [Co.sup.0.8] [Zn.sub.1.2] Z particles, implying single phase of the particles. Low-temperature sintering processing, 900 [degrees]C, was then successfully applied to the single-phase [Co.sub.0.8] [Zn.sub.1.2] Z particles. The coercivities of the [Co.sub.0.8] [Zn.sub.1.2] Z powder and the low-temperature sintered disk were 9 and 20 Oe, respectively, while maintaining the saturation magnetization of 50 emu/g. Index Terms--[Co.sub.2] Z-type hexaferrite, double sintering, low-temperature co-fired ceramic (LTCC), Mossbauer spectroscopy.

Interactions between neighboring cells become increasingly important due to the miniaturization of magnetoelectronic devices. This paper studies the effect of magnetic interaction on the switching behaviors in two different configurations of paired Pac-man shape Permalloy elements: back-to-back and face-to-face configurations. From as-patterned state MFM images, it is observed that the face-to-face configuration is prone to form either two single domains with an antiferromagnetic configuration, one single domain with one vortex or a double vortex configuration. MOKE hysteresis loops show that the coercivity for the face-to-face configuration is smaller than the back-to-back configuration. These experimental results indicate that the back-to-back configuration has weaker interaction between the two Pac-man elements than the face-to-face configuration. We further varied the aspect ratio of Pac-man elements in the pair arrays to tune the magnetic interaction. It was found that the coercivity of pair array increased with the higher cell aspect ratio. Micromagnetic simulation was also performed to simulate the switching process for the two different configurations. Overall, the back-to-back configuration is recommended for applications that demands less inter-cell interactions. Index Terms--Back-to-back, face-to-face, hysteresis loop, magnetic cell interaction, micromagnetic simulation, MRAM, Pac-man shape, switching field distribution.

Magnetization configuration and magnetic switching behavior in two types, P-I and P-11, of submicrometer Pac-man-shaped [Ni.sub.80] [Fe.sub.20] magnetic elements are studied using both magnetic force microscopy (MFM) and numerical simulation. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation-driven switching is replaced by quasi-coherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms. Index Terms--Magnetic domains, magnetooptic Kerr effect (MOKE), magnetization reversal, micromagnetic modeling.

Magnetization configuration and magnetic switching dynamics of submicrometer 'Pac-man'-shaped [Ni.sub.80][Fe.sub.20] elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy (MFM), magnetooptic Kerr effect (MOKE), and micromagnetic simulations. It was found that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct magnetization configurations and magnetic switching mechanisms (in low frequencies), even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal. Fast magnetization reversal is, however, found to be slightly dependent on as-patterned domain configurations. For all elements investigated, the fast reversal leads to very complex nonequilibrium domain configurations. Index Terms--Magnetic hysteresis, magnetization dynamics, magnetization reversal, magnetooptic Kerr effect (MOKE).

Semicoprecipitation and ultrasonic spray pyrolysis (UP) were used to prepare samples of pure and ZnTi-doped spherical barium ferrite particles. The UP process was found to be more effective in controlling spherical shape of BaFe particles. Average particle size was 0.27 to 0.3 micrometer. Particles collected from the UP collector tube showed a single phase of BaFe, while a mixture of alpha-Fe2O3 and BaFe phases was seen in the particles collected from a water-tap bottle.

Several first-principles calculations are conducted to explain the saturation magnetization, as well as the magnetocrystalline anisotropy of the various MnAl permanent magnets. The maximum energy product of the magnet is also determined.

Magnetic properties of sol-gel and conventional ceramic processed [Ba.sub.3][Co.sub.2][Fe.sub.2][O.sub.41] hexaferrite are examined and compared for terrestrial digital multimedia broadcasting (T-DMB) antenna application. The studies have shown that the sol-gel processed and sintered Z-type hexaferrite has met the desired low-loss tan [delta] and broadband for T-DMB antenna.

The impact of the Mn and/or Co doping in Ni-Mn-Co ferrite on the static, dynamic magnetic properties and thermal magnetic stability are examined for high frequency microwave applications up to the gigahertz range. Saturation magnetization and coercivity has increased with increased substitution of Mn and Co and both Mn and Co substituted Ni-Mn-Co ferrite has displayed higher thermal stability factor rather than Ni-Mn and Ni-Co ferrites.

The performance of inverted F meander antenna with a lossy ferrite film is examined and compared to air-core antenna with the same design. Lossy ferrite thin film is shown to be effective in broadening of bandwidth, while retaining an acceptable gain.

Micromagnetic modeling analysis and magnetic force microscopy studies are performed to characterize the magnetization configuration and magnetic switching behavior in two types of submicron Pac-man-shaped Ni80Fe20 magnetic elements. It is observed that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution.

Spherical magnetite nanoparticles were synthesized by the chemical coprecipitation process to study the magnetic properties, particle morphology, and chemically stability. The saturation magnetization of magnetite particles was 49 emu/g at room temperature, which is smaller than that of bulk magnetite due to surface effect.

The magnetic properties of 0.63 un thick, c-axis oriented multilayered and single layered BaM films deposited by rf sputtering on silicon substrates are discussed. The rf sputter deposition method proposed is capable of fabricating BaM think films with high squareness and anisotropy field beyond 1.00 um.

Low temperature synthesis of nanosized lithium zinc ferrite particles by a ball milling process and magnetic properties of zinc substituted lithium ferrite particles are presented. It shows that the saturation magnetization and low coercivity for x-0.7 annealed at various temperatures are discussed in terms of site occupation.

The effects of deposition order and thickness on coercivity of the ferromagnetic bilayers, //Co/Fe and //Fe/Co, deposited on silicon and glass substrates are presented. It shows that the magnetization reversal process is changed from domain-wall motion to magnetization rotation when the coercive force for domain-wall motion in the Fe layer greatly increases due to decreasing saturation magnetization.