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We developed a very sensitive high-frequency carrier-type thin film sensor with a sub-pT resolution using a transmission line. The sensor element consists of Cu conductor with a meander pattern (20 mm in length, 0.8 mm in width, and 18 μm in thickness), a ground plane, and amorphous CoNbZr film (4 μm in thickness). The amplitude modulation technique was employed to enhance the magnetic field resolution for measurement of the high-frequency field (499 kHz), a resolution of 7.10×10−13 T/Hz1/2 being achieved, when we applied an AC magnetic field at 499 kHz. The phase detection technique was applied for measurement of the low frequency field (around 1 Hz). A small phase change was detected using a dual mixer time difference method. A high phase change of 130°/Oe was observed. A magnetic field resolution of 1.35×10−12 T/Hz1/2 was obtained when a small AC field at 1 Hz was applied. We applied the sensor for magnetocardiogram (MCG) measurement using the phase detection technique. We succeeded in measuring the MCG signal including typical QRS and T waves, and compared the MCG with a simultaneously obtained conventional electrocardiogram (ECG) signal.

The present paper reports the principle of a wireless magnetic motion capture system that uses multiple LC resonant magnetic markers and demonstrates its application. Small and lightweight markers (4 mm in diameter, 10 mm in length, and 0.63 g in weight) use a soft ferrite core and a coil, representing a minimal LC circuit with no battery, driven wirelessly by electromagnetic induction. The markers are given respective resonant frequencies ranging from 150 to 450 kHz. The magnetic signal of the marker is detected by a pick-up coil array consisting of 25 pick-up coils. The markers are excited by a superposed wave corresponding to all of the resonant frequencies, while the voltage signals induced through pick-up coils are separated in a frequency spectrum by FFT analysis. Regardless of the number of markers, the voltage amplitude for each resonant frequency can be easily obtained simultaneously, and thus the proposed system can detect multiple markers. In addition, the positional error of the system caused by a mutual inductance between the exciting coil and the LC marker was examined. The impedance change of the exciting coil due to a resonance of the LC marker was found to perturb the strength of the magnetic field used for marker excitation. The closer a marker approaches the exciting coil, the larger it becomes. This fluctuation induces an error in the marker signal, which is measured by the pick-up coils and is necessary for positional calculation. Then, considering the mutual inductance, a compensatory process was employed for positional calculation in order to improve the positional accuracy. After compensation, the absolute positional accuracy was determined to be less than 2 mm within 140 mm of the pick-up coil array.

A novel motion capture system using magnetically coupled LC resonant marker have been developed. This system composed from the LC marker, a driving coil and a pickup coil array. The marker consists only of an inductor and a capacitor without battery or electric wires, and driven wirelessly by the action of electromagnetic induction. The position accuracy was around 2 mm when the marker was located within the space of 50 mm apart from the pickup coil array. The system is applicable for highly accurate motion capturing without magnetic shielding because the system is free from the earth field. Additionally, it has a possibility of a multi-point motion capturing because the system allow markers to have an individual frequency band.

The swimming properties of a spiral-type magnetic micro-machine were analyzed theoretically using 3D finite volume method. The basic equations of incompressible viscous fluid flow were integrated. The flow field around the micro-machine was calculated to estimate the swimming velocity, thrust, drag, and load torque of a spiral-type magnetic micro-machine. Good agreement was obtained between the experimental and theoretical results in a low Reynolds number. Therefore, the 3D analysis method without any fitting parameters was judged to be established.

Electro-deposition of Fe–Tb–O films was attempted using ac currents with low frequency. The film composition, especially Tb content of films, was found to be sensitive to the concentration of complex agent, KNaC 4 H 4 O 6 : when KNaC 4 H 4 O 6 =283.47 mM, plated films with very high Tb content reaching 29 at.% were obtained, in spite of the difficulty in electro-deposition of Tb owing to its very low catalytic activity. Coercivity H c and squareness ratio M r / M S of films varied considerably depending strongly on the intensity of ac current i : when i =0.67 A/dm 2 , films with relatively soft magnetic properties of H c =29O e and M r / M S =0.93 were realized.

We have developed a new planar flux sensing coil using multilayer printed wiring board fabrication technique. The coil is useful for high frequency magnetic flux sensing because the coil is sensitive to the magnetic field and insensitive to the electric field. A 1 MHz–3.5 GHz broad bandwidth thin-film permeance meter is developed by using parallel plates with short plate and shielded loop pickup coil combination. We investigated the upper frequency limit of permeance measurement is given by the minimum value of standing wave position at the center of pickup coil.

We proposed a smart actuator using magneto-elastic strain sensor. This actuator was cantilever-shape and composed by the strain sensor, a PZT plate and feedback system. In this smart actuator, a touching force at the free end was kept constant if the end was displaced. The smart actuator was sensitive for the touching force of less than 1 mN.

Although a soft ferrite thin film with high resistivity is to be applied to GHz magnetic devices, a fabrication process with high temperature annealing prevents us from applying to those devices. This contribution reports that soft ferrite films with the permeability of ≈10 at the frequency of 1 GHz can be obtained by PLD method using low-temperature process.

Magneto-optical (MO) Kerr effect of micro-cavities composed of a Co thin film and SiO 2 /SiN multilayer films was investigated theoretically and experimentally. The micro-cavity structure was found to be very effective for enhancing the MO Kerr effect: the MO Kerr rotation angle exceeding 10° at a designated wavelength of light was obtained, the value of which is more than 100 times larger than that of a Co single-layer film. The large MO Kerr effect is caused by the localization of light originating from the multilayer structure.

The relation between the domain wall motion and the eddy current losses of very thin (110)[001] 3% Si-Fe strip-wound cores were investigated. The measured eddy current losses were larger than those estimated using a modified Pry and Bean model in the frequency region 50–500 Hz. It is known that the domain walls of thick (110)[001] 3% Si-Fe strips move nonuniformly in the low-frequency range (0.1–100 Hz), but this frequency range is lower than that usually used for very thin strips. By measuring the flux voltage in every layer, we found that the voltage waveforms were not sinusoidal, even if the secondary voltage waveform of the core was sinusoidal, and the magnitude of the voltage in each layer was not uniform. These results indicate that the domain wall motion of very thin strips is not uniform, even at 50–500 Hz. The nonuniformity of the domain wall motion makes the eddy current losses larger than those estimated by means of the modified Pry and Bean model.

The type and frequency of grain boundaries in rapidly solidified and subsequently annealed ribbons of Fe-6.5 mass% Si alloy have been determined to discuss the origin of high ductility of the annealed ribbons. The electron channelling pattern (ECP) technique for crystallographic orientation determination was applied. Ribbons subjected to slight annealing after the solidification have a random grain orientation distribution and contain higher frequencies (86–87%) of high-energy boundaries or so called random boundaries. On the other hand, rapidly solidified and fully annealed ribbons with a large grain size of 600 μm and {100} texture contain low-energy boundaries such as low-angle and low Σ, coincidence boundaries in high frequencies. Nearly one half of the boundaries are of low-energy type. Some coincidence boundaries such as Σ5, Σ13 and S 25 occur 3–8 times more frequently than those predicted for a polycrystal with randomly oriented grains. Similarly, low-angle boundaries compose 25% of the total boundaries in the fully annealed ribbon. The inverse cubic root Σ dependence of the frequency for the coincidence boundaries has been discussed. The high ductility of fully annealed Fe-6.5 mass% Si alloy polycrystalline ribbons is attributed to a high frequency of the low-energy boundaries with strong resistance to intergranular fracture.

The magnetostriction constants λ 100 and λ 111 and the anisotropy constant K 1 of Mg-ferrites [Mg η ;Fe 1−η ][Mg 1−η Fe 1+η ]O 4 , (η = 0·101, 0·154, 0·184, 0·219) at room temperature, liquid N 2 temperature and liquid He temperature were observed by ferrimagnetic resonance techniques at 9·5 GHz. The signs of the magnetostriction constants λ 100 and λ 111 are always negative and positive, respectively and the magnitudes of these constants increase with decreasing temperature. These constants λ 100 and λ 111 at liquid He temperature are found to be − 14·4 × 10 −6 and 2·4 × 10 −6 respectively, when η is 0·101, and then the magnitudes of those constants decrease linearly with increasing η.

Ribbon-form Sendust was prepared by a roller quenching method. The ribbon dimensions were: 20–110 μm thick, 2–8 mm wide and 5–10 m long. The normal direction of the ribbon plane was parallel to [100] as well as the [110] axes, and no preferential directions existed within the ribbon plane. Magnetic and mechanical properties were also discussed.

The magnetostriction constants λ100 and λ111 of Ni-Zn ferrite Ni1−xZnxFe2O4 single crystals with x equal to 0, 0.07, 0.17, 0.40 and 0.67 were measured by a three terminal capacitance method from liquid N2 to room temperatures. The constants λ100 and λ111 of Ni ferrite at liquid N2 temperature were −43.0 × 10−6 and −20.1×10−6 respectively. The magnitude of the constant λ100 increased with the increase of Zn concentration and took a maximum at x of about 0.33, while the magnitude of the constant λ111 decreased almost linearly with the increase of Zn concentration and then became zero at x about 0.75.

The magnetorestriction constants of CoS 2 single crystal were measured by a capacitance method in a temperature range from liquid N 2 to the Curie temperatures. The constants γ 100 and γ 111 are −1.9 × 10 −6 and 5.7 × 10 −6 at liquid N 2 temperature respectively, and the absolute values of the constants decrease monotonically with the increase of the temperature. The volume magnetorestriction constant δω / δH at 110 K in the ferromagnetic state is 6 × 10 −10 Oe −1 .

Amorphous Fe 100- x B x (11.5 ≦ x ≦ 22) alloys having the invar characteristics were prepared by a single roller quenching method to investigate the magneto-volume effect. Forced volume magnetostriction, ∂ω/∂ H , increased remarkably with decreasing boron content and the maximum value obtained was about 90 × 10 −10 Oe −1 at 11.5 at.% boron. The estimated value of the pressure dependence of the Curie temperature, ∂ T c /∂ P , was considerably large, being comparable to those of crystalline FeNi invar alloys. The ∂ T c /∂ P curve plotted as a function of T c approximately fitted Wohlfarth's expression.

Magnetostriction of iron, cobalt and nickel ternary amorphous alloy ribbons is studied theoretically. The role of many electronic excited states coupled by intra-exchange as well as the spin self-orbit interaction to the ground state seems to be essential to account for the magnetostriction in these alloys.

By rapid quenching techniques polycrystalline silicon-iron ribbons Si x Fe 100- x (3.8 ⩽ x ⩽ 9.3 in weight), 20–150 μm thick and 2–25 mm wide were prepared. After annealing, the grains about 200 μm and a columnar structure with [100] perpendicular to the ribbon plane were observed, in a Si 6.5 Fe 93.5 ribbon, the coercive field was 80 mOe.

The SMFMR technique was used in order to determine the compositional dependence of saturation magnetostriction in Fe-Co amorphous alloys. The Young's modulus was measured and the value of (15.4 ± 0.2) × 10 10 N/m 2 was obtained for almost all the investigated compositions. The uniaxial in-plane magnetic anisotropy K u of the order of 10 4 erg/cm 3 (at 300 K) was obtained from the FMR data.

Coercive force and losses in high silicon iron ribbons are measured. Drastic decreases of 20 mOe in coercive force is obtained by water quenching or field annealing and low iron losses of 0.38 watts/kg is obtained in ribbons which have low coercive force.