• Journal of Magnetics
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• 제18권3호
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• pp.308-310
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• 2013

Translation induced by the field-gradient force is being observed for a single ferromagnetic iron grain and a ferrimagnetic grain of a ferrite sample ($CuFe_2O_4$). From measurements on the translation, precise saturated magnetization of $M_S$ is possible for a single grain. The method is based on the energy conservation rule assumed for the grain during its translation and the grain is translated through a diffuse area under microgravity conditions. The results of the two materials indicate that a field-induced translation of grain bearing spontaneous moment is generally determined by a field-induced potential $-mM_SH(x)$ where m denotes the mass of sample. According to the above translations, the detection of $M_S$ is not interfered by any signals from the sample holder. The $M_S$ measurement does not require m value. By observing translations resulting from fieldinduced volume forces, the magnetization of a single grain is measurable irrespective of its size; the principle is also applicable to measuring susceptibility of diamagnetic and paramagnetic materials.

• 한국전기전자재료학회논문지
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• 제32권5호
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• pp.399-402
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• 2019

The electromagnetic properties of heavy fermion $CePd_2Si_2$ are investigated using density functional theory using the local density approximation (LDA) and LDA+U methods. The Ce f-bands are located near the Fermi energy and hybridized with the Pd-3d states. This hybridization plays an important role in generating the physical characteristics of this compound. The magnetic moment of $CePd_2Si_2$ calculated within the LDA scheme does not match with the experimental result because of the strong correlation interaction between the f orbitals. The calculation shows that the specific heat coefficient underestimates the experimental value by a factor of 5.98. This discrepancy is attributed to the formation of quasiparticles. The exchange interaction between the local f electrons and the conduction d electrons is the reason for the formation of quasiparticles. The exchange interaction is significant in $CePd_2Si_2$, which makes the quasiparticle mass increase. This enhances the specific heat coefficient.

• Current Applied Physics
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• 제18권11호
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• pp.1190-1195
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• 2018

By employing soft X-ray magnetic circular dichroism (XMCD), soft X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES), we have investigated the electronic structure of the candidate zero-moment half-metallic $Mn_3Ga$. We have studied the ball-milled and annealed $Mn_3Ga$ powder samples that exhibit nearly zero magnetization. Mn 2p XAS revealed that Mn ions in $Mn_3Ga$ are nearly divalent for both of the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry. The measured Mn 2p XMCD spectrum of $Mn_3Ga$ is very similar to that of ferrimagnetic $MnFe_2O_4$ having divalent Mn ions. The sum-rule analysis of the Mn 2p XMCD spectrum shows that both the spin and orbital magnetic moments of Mn ions in $Mn_3Ga$ are negligibly small, in agreement with the nearly compensated-ferrimagnetic ground state of $Mn_3Ga$. The valence-band PES spectrum of $Mn_3Ga$ agrees well with the calculated density of states, supporting the half-metallic electronic structure of $Mn_3Ga$.

• 한국자기학회지
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• 제25권2호
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• pp.31-38
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• 2015

최근에 전자구조 계산으로 반쪽금속성을 가진다는 것이 확인된 4원 호이슬러 화합물인 CoFeCrGa와 CoFeCrGe의 (001)표면에서 반쪽금속성의 유지여부와 표면자성을 Full-potential Linearized Augmented Plane Wave 에너지띠 계산방법을 통해 연구하였다. 이를 위해 두 화합물 모두에서 각기 CoFe와 CrGa, 그리고 CrGe로 끝나는 (001)표면을 모두 고려하였다. 계산된 상태밀도로부터 두 화합물의 두가지 절단표면계 모두에서 반쪽금속성이 유지되지 못함을 알았다. 다만 CoFeCrGa에서 CrGa(001) 표면계는 그 상태밀도로부터 거의 반쪽금속성을 가짐을 알았다. 두 계에서 표면이나 표면 밑층의 Co나 Fe, 그리고 Cr 원자의 자기모멘트는 계에 따라 상당히 다른 값을 가졌다.

• 한국자기학회지
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• 제16권1호
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• pp.11-13
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• 2006

[ $M\"{o}ssbauer$ ] spectra of $Ti_{1-x-y}Co_xFe_yO_2(0.01{\leq}x,\;y{\leq}0.05)$ prepared with $^{57}Fe$ enriched iron have been taken at various temperatures ranging from 80 to 300K. The Mossbauer spectrum of $Ti0.94Co_{0.03}Fe_{0.03}O_2$ consists of a ferromagnetic (six-Lorentzian), a paramagnetic phase (doublet) and armorphous phase over all temperature ranges. Isomer shifts indicate $Fe^{3+}$ for the ferromagnetic phase and the paramagneic phase of $Ti_{1-x-y}Co_xFe_yO_2$ samples. It is noted that the magnetic hyperfine field of ferromagnetic phase had the value about 1.5 times as large as that of u-fe. The XRB data for $Ti_{1-x-y}Co_xFe_yO_2$ showed mainly rutile phase with tetragonal structures without any segregation of Co and Fe into particulates within the instrumental resolution limit. The magnetic moment per (Co+Fe) atom in $Ti0.94Co_{0.03}Fe_{0.03}O_2$, under the applied field of 1T was estimated to be about $0.332{\mu}_B$ which is ten times as large as that of $Ti0.97Co_{0.03}Fe_{0.03}O_2,\;0.024{\mu}_B$ per Co atom, suggesting a high spin configuration of Co and fe ions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.331-332
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• 2008

Couplings between electric, magnetic, and structural order parameters result in the so-called multiferroic phenomena with two or more ferroic phenomena such as ferroelectricity, ferromagnetism, or ferroelasticity. The simultaneous ferroelectricity and ferromagnetism (magnetoelectricity) permits potential applications in information storage, spintronics, and magnetic or electric field sensors. The perovskite BiFeO3(BFO) is known to be antiferromagnetic below the Neel temperature of 647K and ferroelectric with a high Curie temperature of 1043K. It exhibits weak magnetism at room temperature due to the residual moment from a canted spin structure. It is likely that non-stoichiometry and second-phase formation are the factors responsible for leakage current in BFO. It has been suggested that oxygen non-stoichiometry leads to valence fluctuations of Fe ions in BFO, resulting in high conductivity. To reduce the large leakage current of BFO, one attempt is to make donor-doped BFO compounds and thin films. In this study, (Bi1-x,Ndx)(Fe1-y,Tiy)O3 thin films have been deposited on Pt(111)/TiO2/SiO2/Si substrates by pulsed laser deposition. The effect of dopants on the phase evolution and surface morphology are analyzed. Furthermore, electrical and magnetic properties are measured and their coupling characteristics are discussed.

• Bulletin of the Korean Chemical Society
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• 제10권1호
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• pp.8-12
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• 1989

The polycrystalline powder of (BaLa)(MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in a nitrogen flowing atmosphere. The powder X-ray diffraction pattern indicates that (BaLa)(MgMo)$O_6$ has a cubic perovskite structure ($a_0$ = 8.019(3) $\AA)$ with 1:1 ordering or $Mg^{2+}$ and $Mo^{5+}$ in the oxide lattice. The infrared spectrum shows two strong absorption bands with their maxima at 600(${\nu}3$) and 365(${\nu}4$) cm-1, which are attributed to $2T_{1U}$, modes of molybdenum octahedra MoO6 in the crystal lattice. According to the magnetic susceptibility measurement, the compound shows a paramagnetic behavior which follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.60(1){$\mu}B$, which is consistent with that of spin only value ($1.73{\mu}B$) for $Mo^{5+}$ ($4d^1$ electronic configuration). From the thermogravimetric and X-ray diffraction analyses, it has been found that (BaLa)(MgMo)$O_6$ decomposes gradually into $BaMoO_4$, $MoO_3$ and unidentified phases above $900^{\circ}C$ in an ambient atmosphere, absorbing about 0.25 mole $O_2$ per mole of Mo ion, which also supports that oxidation state of $Mo^{5+}$ in the (BaLa)(MgMo)$O_6$.

• 한국자기학회지
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• 제16권5호
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• pp.229-233
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• 2006

나노 구조 철띠의 자기적 성질을 일반기울기 근사(GGA)를 채택한 전전자 full-potenial linearized augmented plane-wave(FLAPW)에너지 띠 방법을 이용하여 이론적으로 연구하였다. 세 줄, 다섯 줄, 일곱 줄의 철선으로 이루어진 띠에서 가장자리 줄의 자기모멘트는 2.97 또는 2.98 ${\mu}_B$로 Fe 단일 직선의 값과 비슷하게 포화된 값을 가졌으며, 가운데 선의 자기모멘트는 2.82 ${\mu}_B$로 2차원 격자의 값과 같았다. 일곱 줄로 이루어진 철 띠의 전하밀도나 스핀밀도는 가장자리 영역에서 거의 평평한 분포를 보였는데, 이는 가장자리 원자로부터 배출된 p-전자로 인한 가리기에 의한 것이다. 일곱 줄로 이루어진 철 띠에서 가장자리 원자의 상태밀도는 가운데 원자에 비해 띠폭이 줄어들었는데 이는 가장자리 효과에 의한 띠좁힘 때문이다.

• Journal of Magnetics
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• 제20권1호
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• pp.31-39
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• 2015

Macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by a three-dimensional (3D) model for exchange-coupled Sm-Co/${\alpha}-Fe$/Sm-Co trilayers with in-plane collinear easy axes. These results are carefully compared with the popular one-dimensional (1D) micromagnetic models and recent experimental data. It is found that the results obtained from the two methods match very well, especially for the remanence and coercivity, justifying the calculations. Both nucleation and coercive fields decrease monotonically as the soft layer thickness $L^s$ increases while the largest maximum energy product (roughly 50 MGOe) occurs when the thicknesses of hard and soft layers are 5 nm and 15 nm, respectively. Moreover, the calculated angular distributions in the thickness direction for the magnetic moments are similar. Nevertheless, the calculated nucleation and pinning fields as well as the energy products by 3D OOMMF are systematically smaller than those given by the 1D model, due mainly to the stray fields at the corners of the films. These demagnetization fields help the magnetic moments at the corners to deviate from the previous saturation state and facilitate the nucleation. Such an effect enhances as $L^s$ increases. When the thicknesses of hard and soft layers are 10 nm and 20 nm, respectively, the pinning field difference is as large as 30%, while the nucleation fields have opposite signs.

• 대한화학회지
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• 제24권4호
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• pp.269-279
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• 1980

$t^2_2$ 전자배치를 가진 팔면체 및 일그러진 팔면체 $[V(III)A_3B_3]$형태 착물에 대한 자기모멘트를 계산하는 새로운 방법을 발전시켰다. [A 와 B = O, Cl, N, F 또는 Br]. 이 방법에 의하여 계산한 자기모멘트가 실험치와 비교적 잘 일치한다. 일그러진 팔면체 $[V(III)A_3B_3]$형태 착물의 계산한 자기모멘트는 tetragonal distortion의 크기가 증가함에 따라 감소한다. 자기모멘트에 대한 k (orbital reduction factor), $\xi'$ 및 온도의 영향을 또한 고찰하였다. 쌍극자모멘트 및 편극율에 대한 $^3T_1$ 분자궤도함수의 기여분을 계산하는 새로운 방법을 발전시켰다. 이 방법에 의하여 계산한 $^3T_1$ 분자궤도함수의 기여분은 합리적인 범위안에 들었다.