• Proceedings of the Korean Magnestics Society Conference
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• 2006.11a
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• pp.86-88
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• 2006

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.620-622
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• 1992

Magnetic characteristics of a brushless disk type motor has been analyzed taking into account the magnetization distribution in the rotor magnet. This paper describes a method for calculating the 3D flux density in the air gap and calculates the induced voltage of the windings and the torque betweens the permanent magnet and the amateur current.

• Journal of Magnetics
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• v.12 no.2
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• pp.72-76
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• 2007

We investigate the spin transfer torque in metallic multilayer system by employing Keldysh non-equilibrium Green function method. We study the dependences of the spin transfer torque on the detailed energy configuration of ferromagnetic, spacer, and lead layers. With Keldysh non-equilibrium Green function method applied to a single band model, we explore spin transfer torque effect in various layer structures and for various material parameters.

• Journal of the Korean Geophysical Society
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• v.2 no.2
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• pp.135-142
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• 1999

Interpretations of 3-component magnetic logging data obtained for a reinforced bar as a model of the line of the magnetic dipoles are conducted using a least squared inversion technique. The length of the bar is 1.12 m, sampling interval is 0.05 m, the distance between the bar and the borehole is 0.3 m, and the top of the bar is fixed at 0 m of depth. The bar is set to be approximately vertical. Magnetic anomalies smoothed with FFT are used as input data for the inversion. For the interpretation of magnetic logging data the depth to the top, the length, the magnetic moment per unit length, the direction of the magnetization (declination and inclination), and the bearing and plunge of the line of magnetic dipoles are left as unknown parameters. The comparison of the results obtained from the individual inversion of the horizontal component or the vertical component of the magnetic anomalies, and those from the simultaneous inversion of horizontal and vertical component of the magnetic anomalies shows that there exist some disagreements between each inversion result. The depth to the bottom of the bar, which is actually 1.12 m, is estimated as 1.18 m, and the inclination of the magnetization is estimated as -76°by simultaneous inversion. The negative value of the inclination indicates that the strength of the remnant magnetization is much greater than that of the induced magnetization, so that the direction of the resultant magnetization points to the top of the bar.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.231-236
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• 2000

In order to predict depth of the pile forward modeling and inversion of magnetic logging data was conducted by using a finite line of dipoles model. The horizontal component as well as the vertical component of magnetic fields can be measured in the borehole, and the magnetic anomalies can be obtained by subtracting the Earth's magnetic field from the measurement. The magnetic anomalies of the pile are considered as vector sum of induced magnetization due to the Earth's magnetic field and remnant magnetization possessed by steel strings in the pile. The magnetic anomalies are used as input data for inversion from which the length, the magnetic moment per unit length, and the dip angle of the pile can be obtained. From the inversion of synthetic noisy data, and the data obtained from the field model test it is found that the driving depth of the pile can be determined as close to the order of measuring interval (5∼10㎝). It is also found that the resultant magnetic anomalies due to an individual steel string in the pile are almost same as those due to a group of steel strings located at the center of the pile. The magnetic logging method also can be used for locating reinforced bars, pipes, and steel casings.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.262-265
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• 2003

During magnetic inrush or over-excitation saturation of the core in a transformer draws a large exciting current. This can cause mal-operation of a differential relay. This paper proposes a modified current differential relay for transformer protection. In order to cope with the remanent flux at the beginning. the start of saturation of the core is detected and the core flux at the instant is estimated by inserting the differential current into a magnetization curve. Then, this core flux value can be used to calculate the core flux. The proposed relay calculates the core-loss current from the induced voltage and the core-loss resistance; the relay calculates the magnetizing current from the core flux and the magnetization curve. Finally, the relay obtains the modified differential current by subtracting the core-loss current and the magnetizing current from the conventional differential current. The proposed technique not only discriminates magnetic inrush and over-excitation from an internal fault, but also improves the speed of the conventional relay.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.366-366
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• 2010

Single crystalline Fe/NiO bilayers were epitaxially grown on Ag(001) and on MgO(001), and investigated by Low Energy Electron Diffraction (LEED), Magneto-Optic Kerr Effect (MOKE), and X-ray Magnetic Linear Dichorism (XMLD). We find that while the Fe film has an in-plane magnetization in both Fe/NiO/Ag(001) and Fe/NiO/MgO(001) systems, the NiO spins switch from out-of-plane direction in Fe/NiO/MgO(001) to in-plane direction in Fe/NiO/Ag(001). These two different NiO spin orientations generate remarkable different effects that the NiO induced magnetic anisotropy in the Fe film is much greater in Fe/NiO/Ag(001) than in Fe/NiO/MgO(001). XMLD measurement shows that the much greater magnetic anisotropy in Fe/NiO/Ag(001) is due to a 90o-coupling between the in-plane NiO spins and the in-plane Fe spins which causes a switching of the NiO spins during the Fe magnetization reversal.

• Geophysics and Geophysical Exploration
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• v.23 no.1
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• pp.50-54
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• 2020

Herein, the closed-form expressions of the magnetic field due to an axially symmetric body such as a right cylinder, are derived. The magnetic field due to a right cylinder is converted from the gravity gradient tensor using Poisson's relation; the magnetic field induced by a constant magnetization can be obtained from the gravity gradient tensor with a constant density. Because of the axial symmetry of the cylinder, the expressions of gravity gradient tensor are derived in cylindrical coordinate and then transformed into Cartesian coordinates for the three components of the magnetic field using an arbitrary magnetization direction.

• Journal of the Korean Magnetics Society
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• v.19 no.1
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• pp.22-27
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• 2009

Reduction of the critical current density ($J_c$) for STT magnetization switching is most important issue of magnetic tunnel junctions (MTJs) based MRAM. This report describes how to decrease the Jc and will introduce the recent research progresses of STT-MRAM devices with material engineering and structural improvement, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.37-41
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• 2002

In this research, we investigate the properties of membrane and thin film sensor which is using magnetic resonance properties. we expect to $Si_xN_y$ and SiC materials as membrane materials, we measured thin film stress and properties to find the best membrane fabrication condition. Of the two membrane, $Si_xN_y$ thin film is the better than SiC thin film. because of an adequate tensile stress and lower thermal expansion coefficient as sensor structure layer. After performing deposition and patterning thin film sensor material on $Si_xN_y$, we analyzed the magnetic hysteresis and magnetic resonance frequency of sensor. If the magnetic field which is applied in sensor material is removed, magnetization made by magnetic field is transited to elastic mode. moreover. energy radiation is induced during the transition and voltage generates in sensor by energy radiation. At this moment, If voltage generation period is longer, mechanical vibration is induced and signal is generated by mechanical vibration. we also see that as the increase of thin film sensor' length and width, magnetic resonance frequency is decreased.