• Bulletin of the Korean Chemical Society
• /
• 제33권7호
• /
• pp.2341-2344
• /
• 2012

A molecular orbital study is presented of the magnetic coupling in the one-dimensional vanadium oxide $Ba_2V_3O_9$ with a bridge formed by two different types of $VO_4$ tetrahedra. The concept of complementary versus counter-complementary effect has been used to explain the structural origin of the magnetic behavior of the compound. Namely, the observed antiferromagnetic coupling is dominated by the orbital complementarity of the V(1) tetrahedra sharing only one oxygen corner with two adjacent $VO_6$ octahedra. The second type of V(2) tetrahedra does not provide a noticeable contribution to the magnetic coupling due to the orbital counter-complementarity of the bridging ligand.

• Bulletin of the Korean Chemical Society
• /
• 제18권9호
• /
• pp.976-981
• /
• 1997

The magnetic susceptibilities of molybdenum ions with 4d1 electronic configuration in the octahedral crystal field were calculated on the basis of ligand field theory. The experimental magnetic susceptibilities for molybdenum ions, which are stabilized at the octahedral site in the perovskite lattice of Ba2ScMoⅤO6 and Sr2YMoⅤO6, were compared with the theoretical ones. We have tried to fit their temperature dependence of magnetic susceptibility with ligand field parameters, spin-orbit coupling constant ζSO, and orbital reduction parameter κ according to intermediate field coupling and strong field theory. Strong field coupling theory could not explain experimental curves without unrealistically large axial ligand field, since it ignores the mixing up between different state via spin-orbit interaction and ligand field. On the other hand, the intermediate field coupling theory could successfully reproduce experimental data in octahedral and trigonal ligand field. The fitting result demonstrates not only the fact that spin-orbit interaction is primarily responsible for the variation of magnetic behavior but also the fact that effective orbital overlap, enhanced by cubic crystal structure, reduces significantly orbital angular momentum as indicated by κ parameter.

• 대한화학회지
• /
• 제24권2호
• /
• pp.91-100
• /
• 1980

축방향대칭을 갖는 팔면체 $[Ti(III)A_3B_3]$형태 착물의 자기모멘트를 계산하는 식을 유도하여 distortion parameter$({\delta})$, 스핀-궤도 상호작용상수$({\zeta}')$ 및 orbital reduction factor의 실험치를 사용하여 이들 착물의 자기모멘트를 계산하였다. 축방향으로 일그러진 팔면체 $[Ti(III)A_3B_3]$형태 착물의 계산한 자기모멘트가 실험치와 비교적 일치하였다. 팔면체로부터 축방향 일그러짐이 커짐에 따라 그리고 orbital reduction factor가 감소함에 따라 계산한 자기모멘트의 값이 크게 감소하였다. 축방향대칭보다 낮은 리간드장으로 일그러진 팔면체착물의 자기모멘트를 계산하는 방법을 발전시켰으며 계산한 자기모멘트를 기초로 하여 일그러진 팔면체 $[Ti(III)A_3B_3]$형태 착물의 구조를 논의하였다.

• 한국자기학회지
• /
• 제20권5호
• /
• pp.201-205
• /
• 2010

X-선 자기 원형 이색성 측정은 자성물질을 구성하는 원소별 자기적 성질의 측정 및 궤도 자기 모멘트와 스핀 자기 모멘트를 구별하여 측정할 수 있다는 장점으로 인해 여러 가지 자성 신물질 및 다양한 기능성 자성 다층 박막의 연구에 많이 이용되어 왔다. 이 글에서는 이러한 X-선 자기 원형 이색성 현상의 원리 및 실험 방법 등을 설명하겠다. 또한 몇 가지 X-선 자기 원형 이색성을 이용한 최근 몇 가지 연구도 소개하려 한다.

• 대한화학회지
• /
• 제50권4호
• /
• pp.281-290
• /
• 2006

Hybrid DFT 계산 방법을 이용하여 1H-Indene과 Mono-sila-1H-indene 분자의 구조와 특성에 관한 이론적 연구를 수행하였다. 이 분자들의 방향족성 특성 연구를 위하여 MO, 비등방성 자기 민감도 등을 계산하였다. 1H-Indene과 Mono-sila-1H-indene 분자들에 대한 X8-X9 결합의 상대적인 안정도와 특성을 이해하기 위하여 NBO 계산을 수행하였다. 그 결과, 8, 9 위치의 Si 원자들이 C 원자들로 치환되었을 때, p orbital의 기여도가 증가하였다. 이러한 결과는 X8-X9 결합 길이는 하이브리드 오비탈의 p 오비탈 기여도에 크게 영향받는 사실을 보여준다. NBO계산을 통하여 X8-X9로부터 *X8-X9 결합 오비탈로의 비편재화에 기인하는 정량적인 에너지 안정화 세기를 결정하였다. MO 분석 결과 연구 대상 분자들의 방향족성은 3개의 비편재화된 pMO와 2개의 비편재화된 sMO에 의해서 주로 영향 받는다는 사실을 알 수 있었다.

• 한국항공우주학회지
• /
• 제36권11호
• /
• pp.1126-1131
• /
• 2008

본 논문은 궤도 기하학 기반 바이어스 추정기법을 다목적실용위성 1호 및 2호의 자기센서 측정데이터에 적용하여 위성체 태양전지판과 전장박스에서 발생하는 유도자기장 바이어스를 추정한다. 유도자기장 바이어스의 추정과 적절한 보정은 자기센서의 노후화를 대처하고 수명을 최대한 연장하여 정상적으로 위성 임무를 수행을 가능하게 한다.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2005년도 ICCAS
• /
• pp.1641-1644
• /
• 2005

Magnetic actuation utilizes the mechanic torque that is the result of interaction of the current in a coil with an external magnetic field. A main obstacle is, however, that torques can only be produced perpendicular to the magnetic field. In addition, there is uncertainty in the Earth magnetic field models due to the complicated dynamic nature of the field. Also, the magnetic hardware and the spacecraft can interact, causing both to behave in undesirable ways. This actuation principle has been a topic of research since earliest satellites were launched. Earlier magnetic control has been applied for nutation damping for gravity gradient stabilized satellites, and for velocity decrease for satellites without appendages. The three axes of a micro-satellite can be stabilized by using an electromagnetic actuator which is rigidly mounted on the structure of the satellite. The actuator consists of three mutually-orthogonal air-cored coils on the skin of the satellite. The coils are excited so that the orbital frame magnetic field and body frame magnetic field coincides i.e. to make the Euler angles to zero. This can be done using a Neural Network controller trained by PD controller data and driven by the difference between the orbital and body frame magnetic fields.

• 한국초전도ㆍ저온공학회논문지
• /
• 제25권2호
• /
• pp.1-4
• /
• 2023

Over the past decade, the exploration of high-temperature superconductivity and the discovery of a wide range of exotic superconducting states in Fe-based materials have propelled condensed matter physics research to new frontiers. These materials exhibit intriguing phenomena arising from their multiband electronic structure, strongly orbital-dependent effects, extremely small Fermi energy, electronic nematicity, and topological aspects. Among the various factors influencing their superconducting properties, high magnetic fields play a crucial role as a control knob capable of disrupting the subtle balance between the spin, charge, lattice, and orbital degrees of freedom, leading to the emergence of various exotic superconducting states. In this review, we provide an overview of the current understanding of the exotic superconducting states observed in Fe-based superconductors, with a particular focus on FeSe and Sr₂VO₃FeAs, under the influence of high magnetic fields.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2009년도 정기총회 및 동계학술연구발표회
• /
• pp.72-73
• /
• 2009

First-principles calculations were carried out to investigate the effects of Al impurities on bcc Fe magnetism by considering SOC. No significant solid solution hardening effect was found. Albeit the effects of the SOC by Al on spin magnetic moments were minor, there are sizeable orbital magnetic effects. It is concluded that the orbital magnetism due to the Al impurity is strongly related with the impurity screening of the system as seen in Si impurity case [3], but the effects of Al impurity is stronger than those of Si impurity in terms of orbital magnetism.

• 한국자기공명학회논문지
• /
• 제22권4호
• /
• pp.101-106
• /
• 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.