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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Magnetics Society
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Journal DOI :
The Korean Magnetics Society
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Volume 1, Issue 2 - Nov 1991
Volume 1, Issue 1 - Jun 1991
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The Electronic and Magnetic Properties of Fe Overlayers on W(110)
;;A. J. Freeman;
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 1~8
The electronic and magnetic structure of Fe overlayers on W(110) is determined by means of the all-electron local spin density full potential linearized augmented plane wave (FLAPW) method with a single slab approach. Charge and spin densities, magnetic moments, contact hyperfine fields, and layer projected density of states (LDOS) are presented. For bilayer Fe coverage, we find magnetic moments to be 2.90 and 2.30
for the surface and subsurface Fe layers, respectively, corresponding to a 18% enhancement of the total magnetization compared with the calculated bulk value (2.22
);For monolayer coverage the moment is 2.56
which is enhanced by 16% compared to bulk. Unusual changes in the magnetic hyperfine interaction are found in going from a monolayer to a bilayer coverage. Comparison of the results to the theoretical ones of the clean Fe(110) to discuss the hybridization and the negative pressure effects. We discuss our results by comparing them to experimental results.
Enhancement of Fe Magnetic Moments in Ferromagnetic
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 9~14
In order to investigate electronic and magnetic properties of
ferromagnet, we have performed electronic structure calculations employing the self-consistent local density functional LMTO(linearized muffin tin orbital) band method. We have obtained the ground state parameters, such as band structures, density of states, Stoner parameters, and magnetic moments. Based on these results, we have investigated microscopically the magnetic structure and the enhancement of Fe magnetic moments in this compound. Magnetic moments of 3 types of Fe(Fe I, Fe II and Fe III) in
are 2.13, 2.50, and
, respectively. Large enhancement of Fe magnetic moment is observed in Fe II and Fe III, which are located rather far from N. This implies that local environment is very important in determining the Fe magnetic moments in this compound. Our value of average magnetic moment per Fe atom.
, is a bit smaller than the reported estimate,
, from the experiment.
Magnetic Properties of the
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 15~21
The magnetic properties of the
superconductor were studied as a function of Sn concentration by utilizing both the vibrating sample magnetometer (VSM) and torque magnetometer. Unlike the cases where Fe and Co were substituted for Cu, the superconducting transition temperature was maintained above 90 K until x reached the value of 0.36. The lower critical field
and upper critical field
are measured as a function of temperature and external magnetic field, respectively. By aid of these results,
), the coherence length
, the penetration depth
, and the Ginzburg-Landau parameter k were oqtained. Flux pinning was also observed in the sample.
Influence of Sputtering Condition on the Deposition Rate, the Microstruture and Magnetic Properties of Pure Iron Thin Film
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 22~30
Study on Heterogeneous Structures and High-Frequency Magnetic Properties Amorphous CoZrNb Thin Films
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 31~36
Structural and compositional heterogeneities of sputter deposited, amorphous
thin films were investigated using TEM and EDS with windowless detector. The films deposited with substrate bias and annealed in rotating magnetc field showed two amorphous phases of Co-rich region and (ZrNb)oxide-rich region, and revealed 'ultra-soft' magnetic properties. Revesible bias-responses and overdamped frequency responses, along with small Hc, Hk and Mr/Ms ratio, give the possibility of ultra-soft magnetic behavior fo CoZrNb thin films. We proposed the vortex type magnetization distribution in remanent state which was correlated with the thin film heterogeneity. Then, the ultra-soft characteristics of the compositionally heterogeneous films were explained by the spin vortices that minimized the total magnetostatic and exchange coupling energies.
Grain Size Dependence of Soft Magnetic Properties in
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 37~41
alloys were prepared by using rapidly quenching techinque and were annealed above their crystallization temperatures. Coercive force, initial permeability and AC power loss of the annealed
alloys have been studied systematically. Nanocrystallines are formed in the annealed alloys which include Mo and Nb. Remarkably improved soft magnetic properties are obtained in the alloys whose average grain size is around 10 nm. However, soft magnetic properties of the alloys are degraded when grain size is less than IOnm or larger than 15nm. It is considered that the degradation of soft magnetic properties in the alloys whose average grain size is less than 10 nm is due to the Fe-rich amorphous phase retained at grain boundary during the initial crystallization process.
Study on Basic Magnetic Characteristics in New Magnetic Materials(2) - Magnetic Properties of Amorphous
alloy Measures with Pulse Method
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 42~48
The basic soft magnetic characteristics of a typical Fe based amorphous
alloy were measured with pulse metheod. Quantitative relations between magnetostriction, anisotropy energy, reluctivity were investigated. The relative contribution factor of magnetostrictive and uniaxial anisotropy energy to the reluctivity were calculated. The internal stress and induced anisotropy were estimated. A tension applied to the long axis of the sample greatly enhanced induced anisotropy.
The Material Constants and Microwave Absorbing Characteristics of ferroxplana Composite Microwave Absorber
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 49~54
In this study the correlation between material constants and microwave absorbing characteristics of ferroxplana composite microwave absorber used in X-band was investigated. The real part of permeability(
) was decreased and the imaginary part of permeability(
) of ferroxplana composite was increased with increaing ferroxplana loading ratio(F/R). The frequency showing maximum attenuation was shifted to lower frequency with increasing absorber thickness. The absorber 2.6 mm thick showed good band width property and 3.2 mm thick showed good attenuation property. From the apphcation of ferroxplana composite's material constants to the region of material constants which satisfy broad band width, it is found that the absorbing characteristics were estimated quantitatively. Estabhshment of material constants' region which satisfies broad band width can make practical application to design of high performance ferrite microwave absorber.
A Study on the Magnetic Properties of Amorphous Fe-Co-RE-B (RE=Nd, Sm, Gd, Tb) Alloys
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 55~59
The temperature-dependent magnetization curves of amorphous Fe-Co-(Nd, Sm, Gd, Tb)-B alloys were measured using a vibrating sample magnetometer from 77 K up to 900 K. The spin wave stiffness constants and the range of the exchange interaction were calculated from the saturation magnetization values at 0 K. Curie temperatures and the Bloch coefficients estimated from the saturation magnetization curves. The low temperature dependence of magnetization is in good agreement with Bloch relation,
. The spin wave stiffness constant and the range of exchange interaction are decreased by substitution of heavy rare earth (Tb, Gd).
Compositional Effect on the Magnetic Properties of Nd-Fe-Co-B and Nd-Fe-Co-Zr-B Bonded Magent
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 60~68
In compacting the melt-spun
magnetic powders. the difference in composition induces a different behavior of closed packing rate as a function of aspect ratio of the powders. The
alloy having a low Co/Fe ratio (low density) shows the better green density to have an enhanced closed packing rate. An empirical power equation relating the green density with the compacting pressure was obtained such as
alloy having a high Nd/Fe ratio possesses much finer grain size(50~60 nm) than that of
alloy and shows the higher coercivity(
). The higher Nd/Fe ratio in the melt-spun Nd-Fe-Co-B alloy, where the domain wall pinning mechanism was found to be predominant, assists the formation of Nd-rich grain boundary phase acting as a pinning site. The grain boundary ranges over
thick in the Nd-Fe-Co-B alloy while it ranges over
thick in the Nd-Fe-Co-Zr-B alloy.
Effects of Disk Surface Velocity on the Microstructures and Magnetic Properties of Anisotropic
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 69~73
The effects of disk surface velocity on the microstructures and magnetic properties of
melt-spun ribbons were investigated. From the X-ray diffraction results. it is confirmed that the lower the surface velocity (
), the better the orientation of c-axis normal to the ribbon plane. The results of magnetic property measurements for the powder solidfied in magnetic field showed that the highest remanence was obtained from the alloy quenched at medium velocity of
. The remanence of the powder solidfied in magenetic field was about 10 % higher than that of the powder solidfied in non-magnetic field.
Effect of Recording Density On the Reproducin Voltage in Perpendicular Magnetic Recording System
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 74~78
The method for analyzing the recording and reading process of magnetic recording system by numerical simulation is introduced. which can simulate the effect of elements of the magnetic recording system. During the whole simulation, hysteresis characteristics must be included. Preisach model and finite element method are used to construct the algorithm. From the wave of recording current, recorded pattern of magnetization in recording media is simulated in recording process, and then waveform of reading signal in head coil is obtained in reading process. To show the validity of this method, this is applied to perpendicular magnetic recording system. Waveform of recording signal and reproduced signal is obtained in several density. Pattern of reprocuced voltage magnitude according to increase of recording density shows roll-off curve.
Finite-EIement Analysis with Localized Functional for Alternating Magnetic Field Problems
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 79~84
A variational approach employing localized functional is presented to solve alternating magnetic field problems with open boundary. The functional used in the approach consists of the domain integral of finite element region only and the boundary integral of the interfacial boundary between the finite and infinite element regions. The boundary integral is obtained by transforming the infinite domain integral for the infinite element region into the interfacial boundary integral. The proposed algorithm is then applied to a simple two-dimensional problem where the analytic solutions are available. It is shown that the algorithm makes it possible to yield good agreements between the numerical and analytic solutions. and that it requires less computer storage memory and computation time than the conventional finite element method due to the reduction of the computing region.
Study on Basic Magnetic Characteristics in New Magnetic Materials
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 85~88
A high sensitive magnetometer using piezoelectric torque sensor was built. The torque produced on the magnetizde sample with small oscillating magnetic field was measured by a piezoelectric sensor. The torque is proportional to the magnetization of the sample. Errors of the measurement for saturation magnetization remain less than 5 % compared to existing standard values.
Non-Contact Magnetoelastic Torque Sensor Using Amorphous Alloys
Journal of the Korean Magnetics Society, volume 1, issue 2, 1991, Pages 89~93
A new kind of a non-contact torque sensor which uses the difference of the maximum magnetic inductions as measurand was constructed. The torque sensor utilizes the tensile and compressive stress of two cores which are attached on the rotating shaft. This sensor shows that the linearity was better than 1 %, and the transient torque can be measured at the sampling rate of 10 kHz which is the same as magnetizing frequency of the core.