• Proceedings of the KOSOMBE Conference
• /
• v.1992 no.05
• /
• pp.64-67
• /
• 1992

To improve signal-to-noise ratio in sodium image, short echo time (2-3 ms) and long data acquisition (10-20 ms) protocols are used. Sodium in biological specimens demonstrates a bi-exponential decay of transverse magnetization and the fast decaying component of the sodium signal results in the reconstruction of images which are blurred significantly. The spatially-dependent nature of the blurs are due mainly to the presence of short local transverse relaxation values (0.7-3 ms) of sodium in tissue. We present an algorithm that corrects for object-dependent blurs due to fast-decaying T2 and improves the computational behavior of the algorithm by incorporating a relaxation parameter into the iterative process.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.12a
• /
• pp.44-45
• /
• 2007

We have studied the formation of alloy for $Ni_{45}AL_{45}C_{10}$ as a function of milling times. This alloy was produced using mechanical alloying. The effect of milling time on local structural changes of $Ni_{45}AL_{45}C_{10}$ has been investigated by means of EXAFS. Both XRD and EXAFS patterns from mechanically alloyed $Ni_{45}AL_{45}C_{10}$ powder indicates the formation of solid solution. The variation of lattice parameter and particle sizes could be analyzed from the different of milling times. Magnetization was also measured by using VSM.

• Journal of Magnetics
• /
• v.12 no.4
• /
• pp.152-155
• /
• 2007

Spin dependent transport was investigated in lateral $Py(Ni_{81}Fe_{19})/Au/Py$ spin valve devices. Clear spin valve effect was observed in conventional four-terminal measurement geometry. Higher resistance was found in antiparallel magnetization field of two Py electrodes which is determined by anisotropy magnetoresistance (AMR) measurements. The rectangular shape of spin signal together with good agreement of switching field convinces observed spin valve signal is resulted from effective spin injection and detection. The magnetoresistance ratio decays exponentially with channel length by which spin diffusion length of Au channel was estimated to be 76 nm.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.47.1-47.1
• /
• 2013

Supersonic turbulence is believed to decay rapidly within a flow crossing time irrespective of the degree of magnetization. However, this consensus of decaying magnetohydrodynamic (MHD) turbulence relies on local isothermal simulations, which are unable to investigate the role of global magnetic fields and structures. Utilizing three-dimensional MHD simulations including interstellar cooling and heating, we investigate decaying MHD turbulence within cold neutral medium sheets embedded in warm neutral medium. Early evolution is consistent with previous studies characterized rapid decay of turbulence with the decaying time shorter than a flow crossing time and power-law temporal decay of turbulent kinetic energy with slope of -1. If initial magnetic fields are strong and perpendicular to the sheet, however long term evolutions of kinetic energy shows that a significant amount of turbulent energy still remains even after ten flow crossing times, and decaying rate is reduced as field strengths increase. We analyse power spectra of remaining turbulence to show that incompressible, in-plane motions dominate.

• Journal of the Korean Ceramic Society
• /
• v.35 no.10
• /
• pp.1014-1019
• /
• 1998

As results of the study on the sinterbility of YIG at the low temperature using CuO as additive CuO com-pound which contain {{{{ { {Fe }_{2 }O }_{3 } }} was shown liquid in sintering process. YIG crystal dissolved into CuO compound liquid phase and then Y element which is considered no solubility in solid CuO compound moved to the grain during cooling. The abnormal grain growth up to 150${\mu}{\textrm}{m}$ at CuO 8.6mole% was shown due to shape accomdation reaction and local liquid distribution. The apparent density of YIG shows minimum at CuO 8.6 mole% due to abnormal grain growth and the saturation magnetization decrease dramatically at 32.5mole% due to orthoferrite formation.

• Journal of Magnetics
• /
• v.18 no.3
• /
• pp.225-229
• /
• 2013

We report a measurement for the anomalous Nernst effects induced by a temperature gradient in [CoSiB/Pt] multilayer films with perpendicular magnetic anisotropy. The Nernst voltage shows a characteristic hysteresis which reflects the magnetization of the film as in the case of the anomalous Hall effects. With a local heating geometry, we also measure the dependence of the anomalous Nernst voltage on the distance d from the heating element. It is roughly proportional to $1/d^{1.3}$, which can be conjectured from the expected temperature gradient along the sample from the heat equation.

• Journal of the Korean Magnetics Society
• /
• v.10 no.5
• /
• pp.225-231
• /
• 2000

The crystallographic and magnetic properties of the sample F $e_{0.8}$ $Co_{0.18}$(BN)$_{0.02}$ synthesized by microwave arc-melting with the maximum power of 3.5 kW have been studied by the methods of an X-ray diffraction and the measurement of the magnetic hysteresis using the vibrating sample magnetometer at room temperature. The samples were prepared in a form of pellet pressed under the pressure of 9,000 N/c $m^2$, rolled coldly, and treated with the different temperatures. The X-ray diffraction pattern of pelleted sample shows that the crystal structure of the sample is bcc as same as that of Fe with a good uniformity. The X-ray diffraction pattern shows that a residual stress, which exists in the sample, is eliminated by final 90$0^{\circ}C$ annealing. As rolling rate and heat treatment temperature increases, the saturation magnetization and the remanence of the samples increase whereas the coercivity of the samples shows decrease. Also the saturation magnetization and the remanence of the samples were affected by rolling rate and rolling direction than heat treatment temperature, but the coercivity of the samples was affected by rolling rate and direction as well as heat treatment temperature. This means that a domain wall motion is easy due to elimination of a residual stress and an inclusion which exists in the sample by rolling and heat treatment and a local induced-magnetization easy axis was also formed to parallel to the rolling direction due to creation of the like-atom pairs across the slip plane by rolling......

• Korean Journal of Materials Research
• /
• v.2 no.2
• /
• pp.143-150
• /
• 1992

Crystal structures and magnetic properties of annealed Co-(Al-Fe) alloys have been investigated. Annealed specimens showed superparamagnetism when x=0.05 and ferromagnetism when $x{\geq}0.10$. Magnetization increased as x increased. X-ray diffraction data revealed that specimens were single-phase in B2(CsCl) structure with constant lattice parameter $2.87{\AA}$. The experimental results were analized on the point of view of the local environmental effect of magnetic atoms.

• Proceedings of the KIEE Conference
• /
• 1994.07b
• /
• pp.1333-1335
• /
• 1994

The nitrification of pure iron powders is found to occur even at room temperature by high energy ball milling in $NH_3$ gas atmosphere. The powders of metastable iron nitrides ($0<at.%N{\le}23.3$) thus produced are identified as the super-saturated bee structure for the N content below 14.9 at.%N and the high temperature phase of the hcp structure above 19.4 at.%N. The atomic volume of Fe in the bcc phase is found to be smaller than that of the N-martensite reported in the literature. Magnetization at room temperature gradually decreases with increasing the N concentration in contrast to the enhancement reported for the bet nitrides. Neutron diffraction experiment also provide detailed information about the local structure surrounding the nitrogen atom. The coordination number of Fe atom around a nitrogen atom for the iron nitride containing 9.5 at.%N turns out to be 3.9 atoms.

• Progress in Superconductivity and Cryogenics
• /
• v.24 no.2
• /
• pp.19-22
• /
• 2022

We studied the effect of substrate-induced strain state on the superconducting transition in GdBa₂Cu₃O_7-x(GdBCO)/La_0.7Sr_0.3MnO₃ (LSMO) bilayers deposited on a LaAlO₃ (LAO) substrate. The stain state of LSMO is controlled by increasing the thickness from 20 nm to 80 nm. Analyses on the extended X-ray absorption fine structure (EXAFS) measurements reveal difference in the direction of MnO₆ octahedral distortion depending on the LSMO thickness, which leads to a difference in anisotropy of magnetization of LSMO layer. The superconducting transitions of our system are strongly correlated with the magnetic anisotropy accompanied by the MnO₆ octahedron distortion in a specific direction. This result suggests the possibility of improving the superconducting transition in the GdBCO/LSMO bilayer system by controlling the degree of competition between superconductivity and ferromagnetism via adjusting strain state in the LSMO layer.