分子合金で磁気モーメントが薄められている - 分子コンドーシステム
Yuki Idobata1, Biao Zhou, Akiko Kobayashi
1Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui, Tokyo 156-8550, Japan.
Journal of the American Chemical Society
|December 23, 2011
まとめ
研究者らは, [Ni{1-x) Cu{x) }{tmdt}{2} を用いて分子コンドーシステムを調査し,より高い銅濃度で反鉄磁気相互作用を観察した. 磁気異常にもかかわらず,コンドの特徴的な抵抗性最小値は4.2Kまで検出されませんでした.
科学分野:
- マテリアルサイエンス 材料科学
- 凝縮物質物理学 凝縮物質物理学
- 分子電子 (モレキュラー・エレクトロニクス)
背景:
- 新しい電子特性を探すために分子システムを調査する.
- 金属有機構造のコンド効果を理解する.
研究 の 目的:
- [Ni{1-x) Cu{x) }tmdt{2}]を用いた分子コンドーシステムを実現し,研究する.
- これらの材料における磁気相互作用と電子伝送を調査する.
主な方法:
- 異なる銅濃度 (x) を有する[Ni{1-x}Cu{x}tmdt{2}]の合成.
- マグネティック感受性 (χT対T) の測定.
- 電気抵抗性 (ρ) の測定は,温度による関数である.
主要な成果:
- 幅広い磁気感受性のピークは,x ≈ 0.15 に対して約10 Kで,シングレット基底状態を示唆しています.
- 2 K 以下の x ≈ 0.27 に対して観測された反鉄磁気相互作用は,π-d 相互作用に起因する.
- 4.2Kまで抵抗性の最小値がないが,8-20Kの間には対数抵抗性の上昇が観察された.
結論:
- この研究は,分子システムにおける磁気相互作用についての洞察を提供します.
- 磁気行動はコンドのような現象を示唆しますが,輸送特性は典型的なコンドシステムと完全に一致しません.
- π−d相互作用と電子輸送の相互作用を理解するためにさらなる調査が必要である.
関連する概念動画
01:26Diamagnetism
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.
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.
01:30Paramagnetism
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...
02:42Valence 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...
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
03:02Colors 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.
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.
01:31Ferromagnetism
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...