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In this study, composite devices were fabricated using ferromagnetic FeSiB-based alloys (Metglas) and ferroelectric ceramics, and their magnetic field sensitivity was evaluated. Sintered 0.95Pb(Zr0.52Ti0.48)O3-0.05Pb(Mn1/3Sb2/3)O3 (PZT-PMS) ceramic exhibited a very dense microstructure with a large piezoelectric voltage coefficient (g31 = −16.8 × 10−3 VmN−1) and mechanical quality factor (Qm > 1600). Owing to these excellent electromechanical properties of the PZT-PMS, the laminate composite with a Metglas/PZT-PMS/Metglas sandwich structure exhibited large magnetoelectric voltage coefficients (αME) in both off-resonance and resonance modes. When the length-to-width aspect ratio (l/w) of the composite was controlled, αME slightly varied in the off-resonance mode, resulting in similar sensitivity values ranging from 129.9 to 146.81 VT−1. Whereas in the resonance mode, the composite with small l/w exhibited a large reduction of αME and sensitivity values. When controlling the thickness of the PZT-PMS (t), the αME of the composite showed the largest value when t was the smallest in the off-resonance mode, while αME was the largest when t is the largest in the resonance mode. The control of t slightly affected the sensitivity in the off-resonance mode, however, higher sensitivity was obtained as t increased in the resonance mode. The results demonstrate that the sensitivity, varying with the dimensional control of the composite, is related to the mechanical loss of the sensor. The composite sensor with the PZT-PMS layer exhibited excellent magnetic field sensitivity of 1.49 × 105 VT−1 with a sub-nT sensing limit, indicating its potential for application in high-performance magnetoelectric sensor devices.

In this study, the influence of low temperature heat treatment on iron loss behaviors has been investigated in 6.5 wt% grain-oriented silicon steels fabricated by a SiO2 textile method. Heat-treatment under hydrogen atmosphere was carried out for 1 hr in the temperature range of 500 to 800°C. As a result, the minimum iron loss was obtained in a sample annealed at 600°C. Transmission electron microscopy analysis showed that B2 and D03 antiphase domains existed in all heat-treated samples but D03 size was maximized after 600°C heat-treatment. In addition, magnetic domains cut through these antiphase boundaries. Therefore, the low iron loss of the sample annealed at 600°C should be ascribed to the reduction in the area of the antiphase boundaries which acted as pinning centers in the magnetic domain walls.

The influence of magnetic annealing on iron loss has been investigated in 0.1-mm-thick grain-oriented high-silicon steels. To prepare such thin high-silicon steels, 0.3-mm-thick commercial electrical steels were mechanically ground to a specific thickness and then annealed at 1200°C under a high vacuum atmosphere. Due to much faster evaporation of Fe than Si, strip thickness decreased and silicon content increased. The 0.23-mm-thick 3% Si samples typically were thinned to a thickness of 0.10 mm, and silicon content increased to 6.5% after annealing for approximately 50 h. The high-silicon steels were further magnetically annealed at 770°C in a dc magnetic field, and an excellent iron loss of around 0.65 W/kg (at 1.5 T/60 Hz) was obtained. The iron loss behavior with both siliconizing and magnetic annealing processes is discussed in the light of microstructural evolution of B2 ordering phases and domain boundary drag effect of surface subsidiary domains.

In this study, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1-mm-thick metal sheets of mu-metal, grain-oriented electrical steel, and nonoriented electrical steel were prepared from commercial alloy sheets through cold rolling and followed high temperature annealing. For magnetic fields generated by three-phase electric currents, mu-metal was the best in shielding performance when magnetic field at the shield point is about 90 ? T, yielding an excellent shielding factor lower than 0.1 in the vicinity of the shield. Above 490 ? T, however, silicon steels were better than mu-metal. Double-layer shielding with grain-oriented silicon steel (inner) and mu-metal (outer) resulted in an excellent shielding factor up to 490 ?T. These results are due to change in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. For magnetic fields by single-phase electric current, on the other hand, a magnetic shield rather increased magnetic field or had no practical effect on shielding performance. This result is explained by superposition of original field vectors and secondary field vectors created by eddy currents within the materials.

Effect of tension coating on iron loss has been investigated as a function of excitation induction and frequency in thin-gauged 3% silicon steel sheets and iron loss after tension coating has been evaluated by loss separation method. In order to additionally reduce iron loss, tension coating without forsterite base coating was applied on surfaces of the thin grain-oriented sheets. Reduction in total loss due to the tension coating results from combination of hysteresis loss and anomalous loss, but the latter plays a major role in the loss reduction. The coated sheets show a maximum iron loss reduction of 18% at an excitation induction of 1.0 T and an excitation frequency of 60 Hz.

Effects of bulk content of sulfur on final texture and magnetic induction have been investigated in 3% silicon iron strips. Within the tested range of sulfur content from 11 to 92 ppm, too high or low sulfur contents resulted in a poor magnetic induction arising from no or a limited {110} texture. A weak {110} texture at a high sulfur content is due to the prolonged time period of {100} or {111} grain growth. Despite the shortened time period of selective growth of {100} or {111} grains, also the weak {110} texture at a low sulfur content is probably attributed to a weak grain boundary pinning effect of the weakly segregated sulfur. A moderate sulfur content provides an appropriate pinning effect enough to suppress {100} or {111} selective growth, finally resulting in a sharp {110} texture.

Hexagonally well-ordered nanoporous anodized aluminum oxide (AAO) templates were synthesized by electrochemical method. Then, magnetite (Fe/sub 3/O/sub 4/) nanoparticles of 8-15-nm diameter were filled in the pores of the AAO template, and then the morphology and magnetic properties were characterized. Vibrating sample magnetometer measurement indicated that the nanoparticles inside AAO showed superparamagnetic behavior at as-filled state. But after annealing at 600/spl deg/C for 2 hr, the nanostructure (i.e., an assembly of nanoparticles) exhibited coercivity of 80 Oe. Superconducting quantum interference measurement device data showed that after annealing the blocking temperature was above 300 K. Thus, the annealed magnetite nanostructures possessed ferrimagnetism.