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A nanofiber nonwoven textile with metallic magnetic material coating was fabricated, and the effect of electromagnetic wave shielding was evaluated. The nanofiber nonwoven textile with an average diameter of about 500 nm was spun by electrospinning. The metallic magnetic material was coated by sputtering on the textile surface. EMI shielding effect of the textile with metallic magnetic material coating was about 90% in the GHz band. Because the textile has thin, light, flexible, and breathable characteristics, it will be versatile for various electromagnetic wave shielding applications. Index Terms--Electromagnetic wave shielding, electrospinning, metallic magnetic material, nanofiber nonwoven textile, sputtering.

It has been very difficult to develop a miniaturized temperature sensor device using the conventional temperature-sensitive ferrites, such as Mn-Zn ferrite, which is due to difficulty of the high-frequency operation, because of their low natural resonance frequency (below 1 MHz) and low electrical resistivity (around [10.sup.2] - [10.sup.4] [OMEGA] x cm). The authors have recently developed a polycrystalline Mn-substituted Li--Zn--Cu ferrite with a high natural resonance frequency beyond 10 MHz and high resistivity over [10.sup.6] [OMEGA] x cm, which exhibited strong temperature-dependent magnetic properties. It was considered that the transmission-line device using a new temperature-sensitive ferrite as an electromagnetic-field propagation substrate enables us to obtain a novel chip temperature-sensing micro device, because of the possibility of high-frequency operation due to a high resonance frequency and high resistivity of the new ferrite. We have simulated a quarter-wavelength resonator using the Mn-substituted Li--Zn--Cu ferrite substrate and its temperature-dependent properties. Since the quarter-wavelength transmission-line resonator includes distributed inductance and capacitance depending on the temperature-sensitive electromagnetic property of the ferrite substrate, this type of device operates as an integrated LC resonator-type temperature sensor. In this study, the integrated resonator-type temperature sensor using a spiral strip-line structure with the Mn-substituted Li--Zn--Cu ferrite substrate was fabricated, and its temperature-dependent characteristics were evaluated. Index Terms--Li--Zn--Cu ferrite, quarter-wavelength resonator, spiral strip line, temperature-sensitive ferrite, temperature sensor.

Magnetoresistance (MR) of current-perpendicular spin valves with nano-oxide layers (NOLs) has been investigated. Insertion of a NOL in a spacer between free and pinned magnetic layers can increase both resistance and MR ratio of the spin valves to the level that satisfies the needs for over 150-Gb/[in.sup.2] recording density. It is shown that the MR enhancement is strongly NOL-material dependent; ferromagnetic CoFe(B) alloys are found to be quite effective in the improvement, while nonmagnetic composites such as TaCu and RuCu degrade the MR ratio. The NOL-thickness dependence of the MR ratio is also measured. It is presented that the CoFe(B) NOL thicker than 1 nm greatly enhances the MR ratio. Nominal-thickness dependence of residual magnetic moment of the NOLs shows that partially oxidized CoFe(B) layers are most effective for the MR enhancement. Little degradation of the free-layer response to an applied magnetic field by the NOL insertion has been observed. From the current-voltage (I-V) characteristic, the electronic transport is revealed to be dominated by metallic conduction rather than tunneling. It suggests that the enhancement stems from the conduction through pinholes. Index Terms--Current perpendicular to plane, giant magnetoresistive heads, oxide layers, spin-valve structures.

Mn-Ir/Fe-Si exchange-coupled films with an Ru underlayer for high frequency applications were fabricated, and their microwave permeability was evaluated. Both exchange bias field and ferromagnetic resonance frequency increased with decreasing Fe-Si thickness. For example, Mn-Ir (10 nm)/Fe-Si (10 nm)/Ru (1 nm) exchange-coupled film deposited on Si[O.sub.2] had a static relative permeability of about 180 and a ferromagnetic resonance (FMR) frequency of about 4.3 GHz. The microwave properties such as permeability and FMR frequency can be controlled by changing Fe-Si thickness. Index Terms--Exchange-coupling, Fe-Si, ferromagnetic resonance frequency, high-frequency micromagnetic devices, Mn-Ir.

A new planar inductor using a composite magnetic core for low voltage and large current dc-dc converter has been developed. The composite material consisted of a 40% volume fraction of Mn-Zn ferrite particle with a mean diameter of 10 [micro]m and polyimide matrix. The composite magnetic core exhibited a low relative permeability of 6. The fabricated planar inductor with a size of 15 x 15 x 1.4 mm consisted of an inner two-turn copper square spiral coil, a top 350-[micro]m-thick composite magnetic core and a bottom 1-mm-thick Ni-Zn ferrite substrate. The inductor had a dc coil resistance of 15 m[ohm] and an inductance of 140 nH. The degradation of inductance was below 4% at a superimposed dc current of 10 A. A synchronous rectifier type buck converter with a switching frequency of 1 MHz, an input voltage of 5 V, and an output voltage of 1 V was constituted using a planar inductor, and exhibited a maximum conversion efficiency of 80% at 4 A. Index Terms--Composite material, dc-dc converter, Mn-Zn ferrite, planar inductor, polyimide, screenprinting.

In order to miniaturize the quarter wavelength transmission-line transformer for high frequency impedance matching, a possibility of a spiral microstrip-line structure with a magnetic/dielectric hybrid structure was investigated. For this purpose, the CoZrNb/polyimide hybrid spiral microstrip-lines with various spiral turns were fabricated and evaluated. From the results, the spiral transmission-line structure enabled to miniaturize the quarter wavelength transformer, whose insertion loss was comparable with that of a straight-line structure. Index Terms--Magnetic/dielectric hybrid medium, quarter wavelength transformer, spiral microstrip-line.

Abstract--A new wideband common-mode noise filter for switching power supplies has been developed. The filter consisted of an Mn-Zn ferrite core and a copper/polyimide tape wound coil. The tape wound coil had two signal lines, two ground lines, and a polyimide dielectric film. The filter exhibited a common-mode rejection of over 30 dB in the wide frequency range of 100 kHz to 100 MHz. The wideband common-mode filtering was due to the high-frequency magnetic loss of the Mn-Zn ferrite core and the optimum ground point selection for the ground lines. Index Terms--Common-mode noise, filter, ground point, magnetic coupling, Mn-Zn ferrite core, switching power supply.

Fe-Si magnetic film and Mn-Ir/Fe-Si exchange-coupled film with an Ru underlayer were fabricated and evaluated. Both coercivity and anisotropy dispersion were reduced due to the Ru underlayer effect on the magnetic properties of Fe-Si magnetic film and Mn-Ir/Fe-Si exchange-coupled film. Even in the Mn-Ir/Fe-Si exchange-coupled multilayer film with an Ru underlayer, the coercivity of the upper Fe-Si layer was reduced. Index Terms--Exchange coupling, Fe-Si, high-frequency micromagnetic device, Mn-Ir, Ru underlayer, small anisotropy dispersion.

The thermal stability and read-write properties of synthetic ferrimagnetic media (SFM) are compared with conventional media (CM) of the same stability factor KuV/kT and Mr[delta] (remanent magnetization and thickness product). SFM are found to be more stable than the equivalent CM, suggesting that the thermal stability advantage does not arise simply from an 'increased effective volume.' The overwrite properties (OW) and nonlinear transition shift (NLTS) are better for CM. However, for media with the same signal decay rate, the OW is similar over a wide head field range and the NLTS match at larger fields. Index Terms--High-density magnetic recording, signal-to-noise ratio, thermal stability, thin film media.