• Journal of the Korean Magnetics Society
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• v.20 no.4
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• pp.129-133
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• 2010

Two-layered ferromagnetic alloy films (NiFe, CoFe) with a Conetic (NiFeCuMo) intermediately soft magnetic layer of different thickness were investigated to correlate the coercivity values and magnetization process with the strength of saturation field of hard axis. Thickness dependence of the $H_{EC}$ (coercivity of easy axis), $H_{HS}$ (saturation field of hard axis.), and X (susceptibility) of NiFe and NiFeCuMo thin films for the glass/Ta(5 nm)/[CoFe or NiFe(5 nm-t/2)]/NiFeCuMo(t = 0, 4, 6, 8, 10 nm)/[CoFe or NiFe(5 nm-t/2)]/Ta(5 nm) films prepared by the ion beam deposition method was measured. The magnetic properties $H_{EC}$, $H_{HS}$, and X of two-layered ferromagnetic CoFe, NiFe films with a NiFeCuMo intermediately super-soft magnetic layer were strongly depended on the thickness of NiFeCuMo layer. The value of the coercivity and magnetic susceptibility of the NiFeCuMo film decreased by 25% and doubled relative to that of the NiFe film.

• Progress in Medical Physics
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• v.18 no.1
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• pp.35-41
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• 2007

In this work practical considerations of a pulsed arterial spin labeling MRI are presented to reliable multi-slice perfusion measurements In the human brain. Three parameters were considered in this study. First, In order to improve slice profile and Inversion efficiency of a labeling pulse a high power Inversion pulse of adiabatic hyperbolic secant was designed. A $900^{\circ}$ rotation of the flip angle was provided to make a good slice profile and excellent Inversion efficiency. Second, to minimize contributions of a residual magnetization be4ween Interleaved scans of control and labeling we tested three different conditions which were applied 1) only saturation pulses, 2) only spotter gradients, and 3) combinations of saturation pulses and spotter gradients Applications of bo4h saturation pulses and spoiler gradients minimized the residual magnetization. Finally, to find a minimum gap between a tagged plane and an imaging plane we tested signal changes of the subtracted image between control and labeled Images with varying the gap. The optimum gap was about 20mm. In conclusion, In order to obtain high quality of perfusion Images In human brain It Is Important to use optimum parameters. Before routinely using In clinical studios, we recommend to make optimizations of sequence parameters.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.38-44
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• 2004

The iron doped colossal magnetoresistance materials with La-Ba-Mn-O perovskites structure have been synthesized by chemical reaction of sol-gel methods. Their crystallographic and magnetic properties have been studied with x-ray diffraction, VSM, RBS, Mossbauer spectroscopy, and magnetoresistance measurements. The crystal structure of the La$\_$0.67/Ba$\_$0.33/Mn$\_$0.99/Fe$\_$0.01/ $O_3$ at room temperature was determined to be orthorhombic of Pnma. The lattice parameters a$\_$0/ and c$\_$0/ increased gradually, but b$\_$0/ deceased with increase of iron substitution. The magnetization and coercivity deceased, also the Curie temperature decreased from 360 K as x increased from 0.00 to 0.05. Magnetoresistence measurements were carried out, and the maximum MR ($\Delta$$\rho$/$\rho$(0)) was observed at 281 K, about 9.5 % in 10 kOe. The temperature of maximum resistance (R$\_$MAX/) decreased with increasing substitution of Fe ions and a semiconductor-metal transition temperature (T$\_$SC-M/) decreased too. This phenomena show that ferromagnetic transition temperature decreased by substituting Fe for Mn ions, it decreases double exchange interaction. This result accords with magnetic structure of neutron diffraction. Mossbauer spectra of La$\_$0.67/Ba$\_$0.33/Mn$\_$0.99/Fe$\_$0.01/ $O_3$were taken at various temperatures ranging from 15 to 350 K. With lowering temperature of the sample, two magnetic phases were increased and finally it showed the two sharp sextets of spectra at 15 K. The isomer shift at all temperature range is about 0.3 mm/s relative to Fe metal, which means that both Fe ions are Fe$\^$3+/ states.Fe$\^$3+/ states.