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相关概念视频

Valence Bond Theory02:42

Valence Bond Theory

Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
Colors and Magnetism03:02

Colors and Magnetism

Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Diamagnetism01:26

Diamagnetism

Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
Types Of Superconductors01:28

Types Of Superconductors

A superconductor is a substance that offers zero resistance to the electric current when it drops below a critical temperature. Zero resistance is not the only interesting phenomenon as materials reach their transition temperatures. A second effect is the exclusion of magnetic fields. This is known as the Meissner effect. A light, permanent magnet placed over a superconducting sample will levitate in a stable position above the superconductor. High-speed trains that levitate on strong...
Ferromagnetism01:31

Ferromagnetism

Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
Paramagnetism01:30

Paramagnetism

Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...

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相关实验视频

Updated: Jun 24, 2026

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene
08:25

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

Published on: July 3, 2015

在CaB2C2中的高温铁磁.

J Akimitsu1, K Takenawa, K Suzuki

  • 1Department of Physics, Aoyama-Gakuin University, Tokyo 157-8572, Japan. jun@phys.aoyama.ac.jp

Science (New York, N.Y.)
|August 11, 2001
PubMed
概括
此摘要是机器生成的。

研究人员发现了CaB2C2,一种新型的高基里温度铁磁体. 这种材料在没有过渡金属的情况下表现出高达770克尔文的铁磁性,挑战了以前关于高温磁性的理论.

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High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings
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High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings

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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
08:55

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

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Last Updated: Jun 24, 2026

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene
08:25

Chemical Vapor Deposition of an Organic Magnet, Vanadium Tetracyanoethylene

Published on: July 3, 2015

High-resolution Thermal Micro-imaging Using Europium Chelate Luminescent Coatings
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Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
08:55

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Published on: June 7, 2018

科学领域:

  • 材料科学 材料科学 材料科学
  • 凝聚物质物理学 凝聚物质物理学
  • 固态化学 固态化学

背景情况:

  • 高基里温度铁磁力通常与过渡金属或稀土元素有关.
  • 添加剂的双价六甲化物,如Ca{1-x) La{x) B6,表现出铁磁性,但具有特定的结构和电子特性.
  • 了解高温铁磁背后的机制对于开发先进的磁性材料至关重要.

研究的目的:

  • 报告发现和描述了一种新型的高基里温度铁磁体,CaB2C2.2.
  • 调查CaB2C2中铁磁性的起源,特别是缺少磁离子的情况下.
  • 为了比较CaB2C2的磁性和电子结构与已知的磁性材料,如双价博化物.

主要方法:

  • 对CaB2C2.2.的实验合成和表征.
  • 测量磁性特性,包括铁磁过渡温度 (Tc).
  • 第一个原则电子结构计算.

主要成果:

  • CaB2C2具有高铁磁过渡温度 (Tc),大约为770克尔文.
  • 在室温下CaB2C2的有序磁矩非常小,大约为每方程式单位10~-4) 波尔磁.
  • 电子结构计算揭示了与二价六合玻化物在费米水平附近的相似性,但CaB2C2具有四角形结构,没有在CaB6中发现的特定带口袋.
  • 结果表明,靠近费米水平的特殊分子轨道对高Tc铁磁起着至关重要的作用,而不是立方结构的三重退化.

结论:

  • 尽管CaB2C2缺乏过渡金属或稀土离子,但它是一种高基里温度的铁磁体.
  • 在CaB2C2中的铁磁性归因于Fermi水平附近的特定分子轨道,而不是在立方六合体中发现的三重退化等结构特征.
  • 这一发现挑战了对高温铁磁的传统理解,并为设计新型磁性材料开辟了新的途径.