• Journal of the Korean Chemical Society
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• v.33 no.5
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• pp.445-451
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• 1989

A series of solid solutions with formula $Er_{1-x}Sr_xFeO_{3-y}, where x is from 0.0 to 1.0, has been synthesized by heating at $1200^{\circ}C$ for 24 hours. X-ray diffraction shows these samples to be orthorhombically distorted perovskites for compositions up to x = 0. 6 and apparantly simple cubic perovskite structures from $0.8{\leq}x{\leq}1.0$. Lattice volumes are increased with the introduction of Sr. The mixed valence state of two kinds of Fe ion in these ferrite systems is analyzed by the Mohr salt titration method. Mossbauer spectra measured at room temperature for x = 0.0 and 0.5 compositions shows hyperfine splitting for iron (III) due to magnetic ordering and indicates that these samples contain octahedrally and tetrahedrally coordinated iron sites. Electrical conductivity measurements indicate that conduction in these samples apparantly occurs over the octahedral sites by a hopping mechanism.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.211-216
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• 2008

The effects of Si impurity on electronic structures and magnetism of bcc Fe are investigated by using a first-principles method by considering spin-orbit coupling. In order to describe the Si impurity, a 27 atomic bcc Fe supercell has been considered. The Kohn-Sham equation was solved in terms of the all-electron full-potential linearized augmented plane wave (FLAPW) method within the generalized gradient approximation (GGA). The effects of spin-orbit coupling were calculated self-consistently by considering spin-diagonal terms based on second variation method. For the ferromagnetic (FM) state without considering SOC, the spin magnetic moment of the Si impurity was calculated to be $-0.143{\mu}B$, while the magnetic moments of Fe atoms were calculated to be $2.214{\mu}B$, $2.327{\mu}B$, and $2.354{\mu}B$ in away from the Si atom, respectively. However, the FM state with considering SOC, the spin magnetic moment of the Si impurity was calculated to be $-0.144{\mu}B$, which is not affected significantly by SOC, but the spin magnetic moments of Fe atoms were calculated $2.189{\mu}B$, $2.310{\mu}B$, and $2.325{\mu}B$, respectively, which are much reduced value compared to those of the FM state without SOC. Comparing the total charge density and spin density, those features are thought to be originated by the screening distortions of the Fe $t_{2g}$ orbital, which can be obtained by considering SOC.

• Journal of the Korean Magnetics Society
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• v.26 no.1
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• pp.1-6
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• 2016

Pd has the highest magnetic susceptibility among single element metals and often shows ferromagnetism under some special environments. In this paper, we report magnetism of 5- and 9-monolayers (ML) calculated by using full-potential linearized augmented plane wave method. Exchange-correlation interaction is taken into account in local density approximation (LDA) and generalized gradient approximation (GGA) and calculational results in LDA and GGA are compared with each other. It is found that calculations by LDA are more reliable compared to those by GGA because LDA prediction of paramagnetism of bulk Pd is consistent with experiments, whereas GGA predicts wrongly ferromagnetim of bulk Pd. Calculational results in LDA on a 5-ML Pd(111) thin film shows a ferromagnetic ground state unlike a paramagnetic ground state of bulk Pd. The center Pd layer of the 5-ML Pd(111) thin film has the largest magnetic moment ($0.273{\mu}_B$) among the layers and |m| = 1 orbital states play a dominant role in stabilizing the ferromagnetism of the 5-ML Pd(111) thin film. A 9-ML Pd(111) thin film in a ferromagnetic state has almost the same total energy as in a paramagnetic state. Since the magnetization of the 9-ML Pd(111) thin film is stable, the ferromagnetic state may be meta-stable.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1302-1307
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• 2018

The crystallographic, electrical and magnetic behaviors of magnetite powder in the vicinity of its Verwey transition were investigated in this study. Magnetite was prepared by synthesizing a nanoparticle precursor and then annealing it at $800^{\circ}C$ for 1 h under a dynamic vacuum. Crystallographic and morphology analyses were done by using scanning electron microscope (SEM) and X-ray diffraction (XRD). The electrical and the magnetic properties were examined by using $M{\ddot{o}}ssbauer$ spectroscopy, vibrating sample magnetometer (VSM) and resistivity measurement. Both the magnetic moment and the resistivity showed discontinuous changes at the Verwey transition temperature ($T_V$). The temperature dependence of magnetic anisotropy constant showed a monotonic decrease with increasing temperature, with slight dip near $T_V$. $M{\ddot{o}}ssbauer$ spectra showed the superposition of two sextets, one from the tetrahedral (A) and the other from the octahedral (B) sites. The results revealed that identical charge states existed in the B site at temperatures both above and below $T_V$. A coordination crossover resulted in a transition from an inverse to a normal spinel at or close to $T_V$.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.512-514
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• 2008

In this paper, a new electromagnetic circuit is proposed for an optical pickup actuator with high sensitivity. Contrary to those of conventional actuators, the proposed circuit has two focusing coils which are diagonally placed at the front and rear of a moving part. The configuration which makes the effective length of the focusing coil longer and the moving part lighter, is helpful in increasing the sensitivity of the actuator. However, the asymmetry of the moving part by two focusing coils causes flexible node vibrations in quite low frequency range. This paper shows that the design modification of the moving part for the reconfiguration of mass moment of inertia can reduce the mode vibrations.

• Journal of the Korean Chemical Society
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• v.26 no.2
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• pp.81-87
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• 1982

The monooxo-bridged binuclear molybdenum(V) complexes, $Mo_2O_3(NCS)_4(Bipy)_2\;(Bipy = bipyridine),\;Mo_2O_3(NCS)-4(Phen)-2$ (Phen = 1,10-phenanthroline), and $Mo_2O_3(NCS)_4(Ox)_2(OxH)_2$ (Ox = oxinato and OxH = oxine) have been prepared. Their electronic and IR spectra, electric conductivity, and magnetic susceptibility were measured. From the results all of th complexes turned out to be electroneutral dimers with about 0.5 BM, and in the oxine complex, $Mo_2O_3(NCS)_2(Ox)_2(OxH)_2$, the oxine seems to bind partly as monodentate and partly as bidentate molecule.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.961-968
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• 2004

In this paper, we present a set of numerical schemes to solve the Muller integral equation for the analysis of electromagnetic scattering from arbitrarily shaped three-dimensional dielectric bodies by applying the method of moments(Mon. The piecewise homogeneous dielectric structure is approximated by planar triangular patches. A set of the RWG(Rao, Wilton, Glisson) functions is used for expansion of the equivalent electric and magnetic current densities and a combination of the RWG function and its orthogonal component is used for testing. Numerical results for a dielectric sphere are presented and compared with solutions obtained using other formulations.

• Journal of the Korean Magnetics Society
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• v.26 no.4
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• pp.124-128
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• 2016

We have investigated the electronic structures of intermetallic multilayer (ML) films of [$Co(2{\AA})/Pd(x{\AA})$] (x: the thickness of the Pd sublayer; x = $1{\AA}$, $3{\AA}$, $5{\AA}$, $7{\AA}$, $9{\AA}$) by employing soft X-ray absorption spectroscopy (XAS) and soft X-ray magnetic circular dichroism (XMCD). Both Co 2p XAS and XMCD spectra are found to be similar to one another, as well as to those of Co metal, providing evidence for the metallic bonding of Co ions in [Co/Pd] ML films. By analyzing the measured Co 2p XMCD spectra, we have determined the orbital magnetic moments and the spin magnetic moments of Co ions in [$Co(2{\AA})/Pd(x{\AA})$] ML films. Based on this analysis, we have found that the orbital magnetic moments are enhanced greatly when x increases from $1{\AA}$ to $3{\AA}$, and then do not change much for $x{\geq}3{\AA}$. This finding suggests that the interface spin-orbit coupling plays an important role in determining the perpendicular magnetic anisotropy in [Co/Pd] ML films.

• Journal of the Korean Chemical Society
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• v.45 no.3
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• pp.242-246
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• 2001

The quaternary thiophosphates, $A_2NiP_2S_6$ (A=Rb, Cs), have been synthesized with halide fluxes and structurally characterized by single-crystal X-ray diffraction technique. These compounds crystallize in the space group $C_{2h}^5-P2_1/n$ of the monoclinic system with two formula units in a cell of dimensions a=5.960(2), b=12.323(4), $c=7.491(3)\AA$, $\beta=97.05(3)^{\circ}$, and $V=546.0(3)\AA^3$ for Rb2NiP2S6 and a=5.957(4), b=12.696(7), $c=7.679(4)\AA$, $b=93.60(5)^{\circ}$, and $V=579.7(5)\AA^3$ for $Cs_2NiP_2S_6.$ These compounds are isostructural. The structure of $Cs_2NiP_2S_6$ is made up of one-dimensional $_\infty^1[NiP_2S_6^{2-}]$ chains along the a axis and these chains are isolated by $Cs^+$ ions. The Ni atom is octahedrally coordinated by six S atoms. These Ni$S_6$ octahedral units are linked by sharing three m-S atoms of the $[P_2S_6^{4-}]$ anions to form the infinite one-dimensional $_\infty^1[NiP_2S_6^{2-}]$ chain. For $Cs_2NiP_2S_6$, the magnetic susceptibility reveals an antiferromagnetic exchange interaction below 8K,which corresponds to the Neel temperature ($T_N$). Above $T_N$, this compound obeys Curie-Weiss law. The magnetic moment, C, and ${\theta}forCs_2NiP_2S_6$ are 2.77 B.M., 0.9593 K, and -19.02 K, respectively. The effective magnetic moment obtained from the magnetic data is agreed with the spin-only value of $Ni^{2+}d^8$(2.83 B.M.) system.

• Journal of the Korean Magnetics Society
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• v.19 no.5
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• pp.165-170
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• 2009

It is well-known that a meta-stable fcc bulk Fe has an antiferromagnetic (AFM) ground state and could be synthesized by growing Fe on a proper fcc metal substrate. In this study magnetism of Fe monolayers on nonmagnetic fcc transition metal (Cu, Rh, Pd, and Ag) (001) surfaces has been investigated using the all-electron full-potential linearized augmented plane wave method. The Fe monolayers on Rh(001) and Pd(001) surfaces were calculated to be stabilized in an AFM state, whereas the Fe monlayers on Cu(001) and Ag(001) surfaces are stabilized in a ferromagnetic (FM) state. Noting that Cu and Ag have the smallest and largest lattice constants and the fcc bulk Fe with a larger lattice constant is getting stabilized in a ferromagnetic state, it is unexpectable and interesting. The calculated magnetic moments of the Fe atoms on Cu, Rh, Pd, and Ag(001) surfaces are 2.811, 2.945, 2.987, and 2.990 $_{{\mu}B}$ in FM states and 2.624, 2.879, 2.922, and 3.001 $_{{\mu}B}$ in AFM states.