• Journal of Magnetics
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• v.1 no.1
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• pp.51-54
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• 1996

The effects of additional P-doping on the magnetic properties, thermal stability and cation distribution of Co-doped ${\gamma}-{Fe_2} {O_3}$have been investigated by means of magnetic annealing and measurements with vibration sample magnetometer and torque magnetometer. It is found that the P-doping promotes the coercivity and its magnetic-thermal stability, which may be attributed to increase of the cubic magneto-crystalline anisotropy constant, $K_1$ and the activation energy, E, for cation rearrangement, respectively. The cation distribution of P and Co-substituted iron oxide was calculated from the variation of the saturation magnetization with P-doping on the basis of the Neel model. It was found that the most of P ions in the iron oxides occupied the B-site of spinel lattice.

• Journal of Magnetics
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• v.5 no.3
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• pp.81-84
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• 2000

A magneto-optical microscope magnetometer (MOMM) has been developed to simultaneously measure 2-dimensional array hysteresis loops of each local area of $320\times320-nm^2$ spots on ferromagnetic films, in addition to grabbing time-resolved domain evolution patterns. Using the system, spatial distribution of local coercivity can be quantitatively generated and then, compared directly with domain patterns grabbed at precisely the same position of a sample. It is clearly demonstrated that local coercivity distribution governs domain reversal behavior via a thermally activated relaxation process.

• Journal of the Korean Magnetics Society
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• v.7 no.4
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• pp.212-216
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• 1997

A pulsed field magnetometer with maximum applied field of 130 kOe has been constructed. The pulsed field generated by a 18 kJ capacitor bank system combined with a pulse coil was damped oscillation with the period of 10.12 ms. Magnetic hysteresis loop was measured by induction method during 10.12 ms of a pulse duration from the first positive to the second positive peak. The difference from DC magnetic properties due to the eddy current effect was inferred below 3% for the NdFeB magnet with the diameter below 5 mm.

• Journal of Magnetics
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• v.2 no.3
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• pp.72-75
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• 1997

The temperature dependent saturation magnetization curve of amorphous Fe67 Co18B14Si1, alloy was measured using a SQUID magnetometer and vibrating sample magnetometer from 5 K up to 800 K. Inelastic neutron neutron scattering measurements also have been used to study the long wavelength spin dynamics of this high Tc amorphous ferromagnetic alloy. The magnon dispersion curve exhibit the conventional quadratic relationship E = D (T) q2 + $\Delta$, typical of an iso=obtained from a low temperature magnetization curve, which was consistent with the value obtained from the analysis oif inelastic neutron scattering data after consideration of its temperature dependence.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.121-146
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• 2000

A novel system of magneto-optical microscope magnetometer (MOMM), capable of simultaneous local problems of magnetic properties as well as real-time magnetic domain evolution imaging of ferromagnetic thin films with 400-nm spatial resolution, New findings in domain reveral dynamics of Co-based multilayers: The reversal ratio of V/R is a governing physical parameter. The activation volumes of wall-motion and nucleation processes are generally unequal. Submicron-scale local coercivity variation determines domain reversal dynamics. A thermally activated relaxation process during domain reversal is existed on the submicron-scale in realistic films. Local variation of magnetic properties should be considered for a realistic simulation. The fantastic capabilities of the MOMM can open many possibilities to broaden and deepen our understanding of domain reversal phenomena in ferromagnetic thin films.

• Bulletin of the Korean Space Science Society
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• 1993.10a
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• pp.8-8
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• 1993

Field-aligned(Birkeland) currents of the High-latitude polar region are to the linkage between the solar wind-magnetosphere system and the ionosphere. The characteristics of field-aligned currents at an attitude of 1300 km have been investigated from the KiSat-A satellite magnetometer data recorded at SatRec form March to May 1993. It is found that the po1arity of both east-west and south-north magnetic components becomes reversed and distorted across the poleward edge. We suggest that these changes May occur rule to the Region 1 and Region 2 currents. It is also suggested that the current time resolution which is about 30 seconds, should be improved to prove gradual polarity changes in the polar region. In addition, it is shown how the observational results depend on the longitude in the high-latitude region.

• Proceedings of the Korean Magnestics Society Conference
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• 1997.05a
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• pp.66-67
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• 1997

• Proceedings of the Korean Magnestics Society Conference
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• 1991.05a
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• pp.37-38
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• 1991

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.145-145
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• 2003

• Proceedings of the Korean Magnestics Society Conference
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• 2003.12a
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• pp.215-215
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• 2003