• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.287.2-287.2
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• 2008

• Journal of Magnetics
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• v.10 no.3
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• pp.122-127
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• 2005

New classes of LC resonators for micro magnetic sensor device were proposed and fabricated. The first type LC resonator (Type I) consists of a small piece of microwire and two cylindrical electrodes at the end of the microwire without direct contact to its ferromagnetic core. In type I resonator the ferromagnetic core of the microwire and cylindrical electrodes act as an inductor and two capacitors respectively to form a LC circuit. The second type LC resonator (Type II) consists of a solenoidal micro-inductor with a bundle of soft magnetic microwires as a core. The solenoidal micro-inductors fabricated by MEMS technique were $500\sim1,000\;\mu{m}$ in length with $10\sim20$ turns. A capacitor is connected in parallel to the micro-inductor to form a LC circuit. A tiny glass coated $CO_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire was fabricated by a glass-coated melt spinning technique. A supergiant magneto-impedance effect was found in a type I resonator as much as 400,000% by precise tuning frequency at around 518.51 MHz. In type II resonator the changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. The phase angle between current and voltage was also strongly dependent on the magnetic field. The drastic increments of magnetoimpedance at near the resonance frequency were observed in both types of LC resonators. Accordingly, the sudden change of the phase angle, as large as $180^{\circ}C$, evidenced the occurrence of the resonance at a given external magnetic field.

• Journal of Magnetics
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• v.14 no.3
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• pp.129-131
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• 2009

A time-coded giant magnetoimpedance (GMI) magnetic field sensor was investigated and designed. The successfully constructed and tested laboratory model demonstrated a sensitivity of 5 ${\mu}s/{\mu}T$ in the field range of $\pm200{\mu}T$. The sensing element in the form of an amorphous thin wire, 100 mm in diameter $\times50$ mm long, was fit into a small field modulation coil of 60 mm length. At a magnetic field modulation in the range of hundreds of Hz, the change in time interval of two adjacent GMI voltage peaks was linearly related to the external magnetic field to be measured. This mechanism improved the sensor linearity to better than 0.3% in the measuring range of $\pm200{\mu}T$.

• Journal of Magnetics
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• v.9 no.2
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• pp.47-51
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• 2004

Giant magneto-impedance (GMI) effect in zero-magnetostrictive Co-based amorphous ribbons samples in their as-quenched and stress-released states as well as with intentionally induced magnetic anisotropy were investigated. Magnetic and impedance properties of the samples exhibiting different anisotropy were compared and the optimum operation conditions for the studied samples from the view-point of their utilization as a sensor element have been determined. A design of a model of magnetic field sensor and characteristics of the constructed prototype are presented.

• Journal of Magnetics
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• v.12 no.1
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• pp.31-34
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• 2007

The Co-based ribbons with different length were annealed in different magnetic field and GMI profiles were investigated in order to clarify the influence of ribbon size on GMI effect. The GMI ratio decreased with the decreasing in length and also decreased with increasing annealing field. While, the slope of GMI profiles inclined and the field range showing linearity was broadened. It shows prospect to low field sensor, especially for a navigation sensor.

• Journal of the Korean Magnetics Society
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• v.17 no.3
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• pp.141-146
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• 2007

A new class of LC-resonator for micro magnetic sensor device was invented and fabricated by means of MEMS technique. The micro LC-resonator consists of a solenoidal micro-inductor with a bundle of soft magnetic microwire cores and a capacitor connected in parallel to the micro-inductor. The core magnetic material is a tiny glass coated $Co_{83.2}B_{3.3}Si_{5.9}Mn_{7.6}$ microwire fabricated by a glasscoated melt spinning technique. The core materials were annealed at various temperatures $150^{\circ}C,\;200^{\circ}C\;,250^{\circ}C\;,$ and $300^{\circ}C$ for 1 hour in a vacuum to improve soft magnetic properties. The solenoidal micro-inductors fabricated by MEMS technique were $500{\sim}1,000{\mu}m$ in length with $10{\sim}20$ turns. The changes of inductance as a function of external magnetic field in micro-inductors with properly annealed microwire cores were varied as much as 370%. Since the permeability of ultra soft magnetic microwire is changing rapidly as a function of external magnetic field. The inductance ratio as well as magnetoimpedance ratio (MIR) in a LC-resonator was varied drastically as a function of external magnetic field. The MIR curves can be tuned very precisely to obtain maximum sensitivity. A prototype magnetic sensor device consisting of the developed microinductors with a multivibrator circuit was test successfully.

• Journal of the Korean Magnetics Society
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• v.13 no.5
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• pp.198-203
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• 2003

To investigate whether the use of hard magnetic film is available to generate bias magnetic field for a magnetoimpedance sensor, the magnetic properties of SmCo hard magnetic films were investigated as a function of their compositions. The saturation magnetization decreased with Sm content increasing in SmCo films. And, the coercive force increased in the extent of Sm content of 28 at%, but decreased as Sm content increased moreover. The bias field effect of SmCo film to amorphous CoZrNb film was investigated with the magnetization corves, permeabilities, and magnetic domain structures of SmCo/CoZrNb multilayers. The bias field of about 60 Oe was observed in the film with 3 mm ${\times}$ 0.5 mm, which can be constructed as a MI sensor, and this result strongly indicates that the bias field generated from a hard magnetic film is adequate to enhance the sensitivity of a MI sensor with hard/soft magnetic multilayer structure.