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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Magnetics Society
Journal Basic Information
Journal DOI :
The Korean Magnetics Society
Editor in Chief :
Volume & Issues
Volume 4, Issue 4 - Dec 1994
Volume 4, Issue 3 - Sep 1994
Volume 4, Issue 2 - Apr 1994
Volume 4, Issue 1 - Mar 1994
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Dynamic Responses in Ultra-Soft Magnetic Thin Films
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 1~6
The magnetization dynamics was investigated by solving possible origins of overdamped susceptibility observed in ultra-soft magnetic amorphous thin films. The experimental high frequency spectrum and computational spectrum calculated from Gilbert's equation of motion were compared in order to find proper damping factor
and demagnetizing coefficients
for ultra-soft magnetic films. A magnetization vortex mode was, then, proposed to explain the origin of the reversible susceptibility and other anomalies of the ultra-soft magnetic heterogeneous thin films. In this mode it is suggested that there occur, within the nanoscale structural features of the ultra-soft films, incoherent rotational spin motions that are highly damped by the energy transfer from short wavelength spin wave modes and local defect structure mode interactions.
Ferromagnetic Resonance Study of a Nanocrystalline
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 7~11
Ferromagnetic resonance experiment was performed to study the variations of micromagnetic structure with heat treatment of melt spun
alloy for 1h at every
in the temperature range of
. The variations of micromagnetic structure was discussed qualitatively in terms of the variations of line width
and resonance magnetic field
. With increasing armealing temperature to
increases due to the decrease in magnetic anisotropy resulting from structural relaxation during heat treatment. With increasing annealing temperature from 400 to
decreases due to the increase in magnetic anisotropy resulting from the formation of nanocrystalline particles embedded in an amorphous matrix. With increasing armealing temperature from 500 to
increases due to the decrease in magnetic anisotropy resulting from the formation of homogeneous nanocrystalline structure with a minor amorphous phase. Further increase in armealing temperature above
to increase and
to decrease due to the increase in magnetic anisotropy due to the formation of inhomogeneous grain structure and intermetallic compounds.
Effet Studies on Nanocrystalline
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 12~19
The crystallization behavior of the amorphous
alloy with isothermal annealing at
was studied by
spectroscopy. The amorphous phase was revealed to coexist together with
nanocrystalline and Cu-duster in annealed alloys by
spectrum analysis. At the early stage of crystallization, Si content of FeSi is high due to the creation of Cu-cluster, and decreases with annealing until 60 minutes, which results in the increase in the mean hyperfine field of FeSi, and thereafter keeps constant. After 60 minutes, the decrease in the mean hyperfine field of the residual armrphous, in spite of a slight change in the volume fraction of the FeSi and the residual armrphous, is caused by the increase in the content of Nb and B in residual amorphous phase. Both directions of the hyperfine field, those of the FeSi and the residual amorphous, become randomly oriented in about 60 minutes. For FeSi and Cu-duster, the Avrami exponents are 0.51 and O.65, the activation energies are 2.35 eV and 2.44 eV, and the incubation times are 2.4 minutes and 0.8 minutes respectively. Earlier formation of Cu-duster than that of FeSi is coincidence with the fact that Cu atom promotes the nucleation of the FeSi.
Effects of Permalloy Multilayered Schemes and CoZrNb Intermediate Layer on Recording Characteristics of CoCr/NiFe Media
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 20~24
The read/write characteristics of CoCr/NiFe double layered media are strongly affected by the magnetic properties of NiFe magnetic soft layer as well as those of CoCr recording layer. Modification of the permalloy layer by NiFe/Ge multilayer scheme resulted in the higher recording sensitivity and the higher reproduced voltage of CoCr/NiFe medium and this is attributed to the higher permeability of the back layer and high perpendicular anisotropy of the CoCr recording layer. Although higher permeability of back layer results in higher recording sensitivity, the increment of the reproduced voltage was not remarkable, which can be confirmed in the FEM numerical analysis. On the contrary, peak shift characteristics of the CoCr/NiFe medium with the NiFe multi back layer was deteriorated compared to that of the CoCr/NiFe medium with NiFe single back layer. Insertion of ferromagnetic thin CoZrNb intermediate layer between CoCr and NiFe layer was effective to ensure large reproduced voltage and low peak shift. These recoridng characteristics were also discussed in connection with microstructural characteristics.
Preparations and Magnetic Properties of Aluminum Anodic Oxidized Films Electrodeposited Cobalt-Iron Alloys
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 25~31
The magnetic properties of aluminum anodized film in which Co-Fe alloy electrodeposited are investigated with regard to the alloy composition of magnetic films. The electrodeposited Co-Fe particles are confirmed to be single phase Co-Fe alloys by X-ray diffractions. At 34 at% Co, the sample with small pore diameter(particle diameter
) has a large magnetic energy product(
) of about 1.44 MGOe due to the large saturation magnetization, the high coercive force and good squareness of the M-H curve. However, for the samples with particle diameter larger than
, the bottom of each particle forms abnormal particle claaed branch-shaped unlike the sample of the particle diameter
. In this case, the magnetic anisotropy energy was about zero at the compositions of 45 and 75 at% Co. Moreover, at the compositions from 50 to 70 at% Co, the anisotropy became negative value. This means that an easy axis of magnetization of the film is in plane in plane in spite of the perpendicular shape anisotropy of the particle. It was found that the bottom extremity of the particle contains FeC from the X-ray diffraction. Thus the effect of the bottom extremity, that is, an unusal magnetic property was removed by electrodepositing Cu at the bottom extremity of the particle. Itis clear that the magnetic properties of the ilms are influenced by he branch-shaped bottom extremity filled with FeC.
Effects of Sputtering Ar Gas Pressure on Magnetic and Magneto-Optical Properties in Compositonally Modulated Co/Pt Superlattice Thin Films
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 32~38
We have investigated the effects of sputtering Ar gas pressure on magnetic and magneto-optical properties in compositionally modulated Co/Pt superlattice thin films. The samples were prepared by dc magnetron sputtering. Sputtrering Ar gas pressure was varied from 2 to 30 mTorr. The microstructure of the samples was examined by scanning electron microscope and the x-ray diffractometry. The magnetization, the Kerr rotation angle, and the reflectivity of the samples were measured. The columnar structure was developed, and the coercivity was drasti- cally increased, when the sputtering Ar gas pressure was higher than 20 mTorr. We explained that the variation of the magnetization, the Kerr rotation angle, and the reflectivity was related with the microstructure influenced by the variation of the Ar gas pressure.
Structural, Magnetic, and Magneto-Optic Properties of Nonstoichiometric Bismuth-Substituted Yttrium lron Gamet Films Prepared by Pyrolysis
Jae-Kyong Cho ;
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 39~43
Polycrystalline nonstoichiometric bismuth-substituted yttrium iron garnet films with cation ratios of Bi:Y:Fe=1.5+u:1.5:5 and Bi:Y:Fe=1.5:1.5+v:5, where
, have been prepared by pyrolysis. The crystal phases formed in these films at various temperatures have been analyzed by high power x-ray diffractometry (XRD). The saturation ma- gnetization, the Curie temperatures, and the Faraday rotation at the wavelength of 633 nm have been measured as a function of u and v. The XRD studies indicated that the bismuth and yttrium depleted (u < 0 and v < 0) films consisted of the mixed phases of garnet and impunity. While in the bismuth and ytrium overdosed films, no impurity lines were observed over a wide composition range of
. The observed magnetic and magneto-optic data of these overdosed films, however, could only be reasonably explained by assuming the presence of samll amount of spurious phases, not detectable by the XRD.
Hall Effect of High
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 44~47
thin film was grown up for c-axis orientation by epitaxial growth method on
single crystal substrate. The crystal structures of this thin film were found to be c-axis orientation by X-ray diffraction patterns. Hall effect and resistivity measurements were made by van der Pauw method. Hall resistivity was calculated from the magnetoresistivity by considering thermomagnetic effect. The relation was
The measured Hall resistivity and the calculated one are in good agreement each other.
NQR Study of the Anisotropy in
B. Chang ; Cheol-Eui Lee ;
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 48~51
We have studied the room temperature anisotropy in the high
by means of the
nuclear quadrupole resonance (NQR). For the magnetically oriented powder samples, NQR signals were obtained only when the RF magnetic field is applied perpendicular to the direction of the crystalline c-axis. Significant differences in the spin-lattice relaxation times (
) and the lineshapes were observed between the unoriented powder sample and the magnetically oriented sample.
Proton and Deuteron Spin-Lattice Relaxation in Gaseous HD
;R. E. Norberg;
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 52~55
The proton and deuteron spin-lattice relaxation times,
, have been measured in HD between 30 K and 313 K in the pressure of 0.67 - 1.92 atm. The nuclear magnetic resonance frequencies are respectively 358.012 MHz for a proton and 58.958 MHz for a deuteron. From the measurements of
the ratio of the correlation times
that are associated with the molecular angular momentum operators was obtained. The nuclear spin-lattice relaxation time at J = 1 state has been observed to have a temperature dependence being proportional to
Characteristic Analysis of the Magnetic Fluid Seal considering the Shape of the Pole Piece
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 56~61
Magnetic fluid is ferromagnetic material in liquid state, so the surface configuration of magnetic fluid affects the magnetic field, and vice versa. To analyze the devices with magnetic fluid, the magnetic field equations and hydrodynamic equation should be solved simultaneously. This paper presents the numerical algorithm to obtain the surface configuration of fluid under the influence of gravity, pressure and magnetic field without conventional sim¬plified assumption. The algorithm consists of nonlinear finite element method and ferro-hydrodynamics, such as Poisson equations and Bernoulli equations, respectively The simulated configurations of fluid are compared with experimental results, and the influence of the amount of fluid and pole piece shape on the seal capacities are analyzed.
Dispersion Characteristics of Oleic Acid Stabilized Water-based Magnetic Fluids by Peptiaztion Method
Journal of the Korean Magnetics Society, volume 4, issue 1, 1994, Pages 62~68
Water-based magnetic fluids containing synthesized ultrafine magnetite were successfully prepared with
fatty acid such as oleic acid, linoleic acid and stearic acid. Oleic acid was needed the amount of
mol per 20 g magnetite to stabilize the magnetite
particles. From pH 8.0 to pH 11.0, stable aqueous-based fluids could be obtained. The aggregated powder after drying the water-based magnetic fluid was also successfully re-dispersed in dilute
solution and in kerosene. The pH levels of the magnetic fluid using oleic acid system could be predicted by the pH values obtained by calculation of therrrodynamic data.