• Bulletin of the Korean Chemical Society
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• v.17 no.9
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• pp.845-849
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• 1996

Bis(N,N-dimethyl-2-aminomethylthiophenium)tetrahalocuprate(Ⅱ) salt, (dmamtH)2CuCl4 and (dmamtH)2CuBr4 were prepared and characterized by spectroscopic (IR, UV-Vis, EPR, XPS), electrochemical method, and magnetic susceptibility measurement. The experimental results reveal that the compounds have pseudotetrahedral symmetry around copper(Ⅱ) site due to the steric hinderance of the bulky 2-(dimethylaminomethyl)thiophene in the complex. The N-H…Cl type hydrogen bonding is expected in (dmamtH)2CuCl4 from the XPS and IR data. Magnetic susceptibility data show that both of the compounds follow Curie-Weiss law in the range of 77-300 K with negative Weiss constant exhibiting antiferromagnetic interaction between copper(Ⅱ) ions in solid state.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1123-1127
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• 1996

Crystalline compound RbV2SeO7, a Rb analogue of KV2SeO7, was synthesized from a hydrothermal reaction of V2O5, V2O3, SeO2, and Rb2CO3 in the mole ratio 3: 1: 15: 6 (in millimoles) at 230℃. RbV2SeO7 crystallizes in an orthorhombic space group Pnma (No. 62) with a=18.444(8), b=5.415(3), c=7.070(4) Å, Z=8. The two structures of KV2SeO7 and RbV2SeO7 are almost the same except that bond lengths in the latter are slightly longer than in the former. The magnetic susceptibility measurement for RbV2SeO7 in the temperature range 4-300 K showed an antiferromagnetic ordering with TN=45 K, higher than that for KV2SeO7 of 27 K. The origin of the magnetic coupling and the different ordering temperatures in the two phases are discussed in relation to the crystal structures.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1153-1158
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• 1997

The powder characteristics of LiMn2O4 prepared by the citrate sol-gel method have been investigated. The optimum pH for the preparation of homogeneous citrate gel was calculated by the theoretical consideration of thermodynamic equilibrium constants for metal-citrate complexes and metal salts. The obtained citrate gel was prefired at 300 ℃ and calcined at 300-700 ℃ for 1 h. The obtained powders were characterized by TG/DSC, FT-IR spectrometer, X-ray diffractometer, SQUID magnetometer, SEM, and particle size analyzer. It was observed that the mixed phases of spinel LiMn2O4 and Mn3O4 were transformed into spinel LiMn2O4 phase and the vibrational bands due to the carbonate and nitrate were also disappeared over 400 ℃. At temperatures below 150 K, inverse molar susceptibilities of every sample began to show an antiferromagnetic ordering of Mn magnetic moments.

• Journal of the Semiconductor & Display Technology
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• v.9 no.3
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• pp.1-4
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• 2010

First-principles calculations based on spin density functional theory are performed to study the spin-resolved electronic properties of AlN doped with a Cu concentration of 6.25%-18.75%. The ferromagnetic state is more energetically favorable state than the antiferromagnetic state or the nonmagnetic state. For $Al_{0.9375}Cu_{0.0625}N$, a global magnetic moment of 1.26 mB per supercell, with a localized magnetic moment of 0.75 $m_B$ per Cu atom is found. The magnetic moment is reduced due to an increase in the number of Cu atoms occupying adjacent cation lattice position. For $Al_{0.8125}Cu_{0.1875}N$, the magnetism of the supercell disappears by the interaction of the neighboring Cu atoms. The nonmagnetic to ferromagnetic phase transition is found to occur at this Cu concentration. The range of concentrations that are spin-polarized should be restricted within very narrow.

• Journal of Magnetics
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• v.16 no.1
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• pp.1-5
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• 2011

The magnetism and electronic structure of bcc $Al_1Fe_{26}$ was investigated by means of first-principles calculations with and without spin-orbit coupling (SOC). From the calculated total energy, the SOC corrected system is shown to be approximately 5 meV per atom lower than the SOC uncorrected system. The induced spin magnetic moment at the Al site was -0.125 ${\mu}_B$ without SOC and -0.124 ${\mu}_B$ with SOC. The orbital magnetic moments were calculated to be 0.002 ${\mu}_B$ in [$\overline{1}$00] direction for Al. The electronic structures showed the nearest neighbor antiferromagnetic interaction between Fe and Al to be essential for determining the magnetism of the $Al_1Fe_{26}$ system.

• Journal of Magnetics
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• v.12 no.2
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• pp.68-71
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• 2007

Even a pure bulk Fe has a complicated magnetic phase and its magnetism is still needed to be clarified. In this study we investigated the magnetism of bcc and fcc bulk Fe with total energy calculations as functions of atomic volume. The full-potential linearized augmented plane wave method was adopted within a generalized gradient approximation. The ground state of bulk Fe is confirmed to be of ferromagnetic (FM) bcc. For fcc structured Fe an antiferromagnetic (AFM) state is more stable compared to FM states which exist as low spin and high spin states. The stable AFM states were found to accompany a tetragonal distortion, while the FM states remained in a cubic symmetry. At an expanded lattice constant a high spin FM state was calculated to be able to be stabilized with significant enhanced magnetic moment compared to the value of the ground state, bcc FM.

• Journal of Magnetics
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• v.12 no.2
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• pp.64-67
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• 2007

Electronic structures of ordered double perovskites $Ba_2MReO_6$ (M=Mn, Fe, Co, and Ni) are investigated by using the linearized muffin-tin orbitals band method in the local spin-density approximation (LSDA) and the LSDA+U method. The half-metallic ferrimagnetic ground states are obtained for M=Fe and Ni in the LSDA+U, whereas the insulating ground state is obtained for M=Mn in the LSDA+U incorporating the spinorbit interaction. For M= Co, the antiferromagnetic ground state is stabilized in the LSDA+U by invoking the structural distortion.

• Proceedings of the Korean Magnestics Society Conference
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• 2016.11a
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• pp.56-57
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• 2016

• Journal of the Korean Magnetic Resonance Society
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• v.22 no.4
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• pp.101-106
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• 2018

Magnetite is the oldest magnet material known to mankind. It is getting attention again from solid state physics researchers now a days because it is one of the most strongly correlated electron systems. Spin, charge, and orbital orders are interplaying with lattice and involved in the Verwey transition where magnetization, conductivity, and structure changes suddenly. The peculiar ordering states above and below the transition temperature mainly originate from the coexistence of $Fe^{2+}$ and $Fe^{3+}$ ions in the B site of the inverse spinel structure. In particular, the state of the charge and orbital order was the oldest and most intriguing problem. NMR has made significant contribution to the investigation of this question. A. Abragam stated that there is no doubt that NMR is a very powerful tool for the study of ferromagnetic and antiferromagnetic materials. In this mini-review, a short history of NMR investigation of magnetite is presented, providing a support to Abragam's claim.

• Journal of Korean Vacuum Science & Technology
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• v.6 no.2
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• pp.76-78
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• 2002

We have carried out the first-principle electronic structure calculations to investigate the spacer layer formation of Fe/Si multilayered films (MLF) and compared with the results obtained by optical spectroscopy. The computer-simulated spectra based on various structural models of MLF showed that neither FeSi$_2$ nor B2O-phase FeSi, which are semiconducting, could be considered as the spacer layers in the Fe/Si MLF for the strong antiferromagnetic coupling. The optical properties of the spacer extracted from the effective optical response of the MLF strongly support its metallic nature. The optical conductivity spectra of various phases of Fe-Si compounds were calculated and compared with the extracted optical properties of the spacer. From the above theoretical investigations it is concluded that a E2-phase metallic FeSi compound is spontaneously formed at the interfaces during deposition.