14Kで磁気ヒステレシスを示すN2(3-) 根架けテリウム複合体
Jeffrey D Rinehart1, Ming Fang, William J Evans
1Department of Chemistry, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|August 16, 2011
まとめ
研究者は,単一分子磁石の行動を示す新しいディランタニド複合体を合成しました. テリビウム複合体は,これまでで最も硬い分子磁石であり,より広範な温度緩和のための効果的な磁気交換結合を示しています.
科学分野:
- 協調化化学について
- マグネト化学 マグネト化学
- マテリアルサイエンス 材料科学
背景:
- 単分子磁石 (SMM) は,高密度データストレージと量子コンピューティングの開発に不可欠です.
- ランタニドイオンは,SMMの重要な特性である強い磁性アニソトロピーを提供します.
- 窒素 (N(2)(3-)) 基幹ブリッジは,金属中心間の磁気交換相互作用を媒介することができます.
研究 の 目的:
- 新しいN(2)(3-) 基幹橋渡し型ディランタニド複合体を合成し,特徴づけること.
- これらの新しい複合体の磁気特性,特にSMMの振る舞いを調査する.
- 磁気交換を媒介し,SMMのパフォーマンスを向上させるためのN(2)(3-) 基幹ブリッジの役割を調査する.
主な方法:
- 3つのディランタニド複合体の合成: {[(Me(3) Si) (((2) N] (((2) ((THF) Ln} (((2) ((μ-η(2):η(2) -N(2)) (((-) (Ln = Tb, Ho, Er).
- マグネット感受性,磁気ヒステレスなどの磁気特性測定.
- ラジカル・ブリッジの効果を明らかにするために,非ラジカル・ブリッジのアナログとの比較.
主要な成果:
- 3つの合成されたディランタニド複合体はすべて,単分子磁石の振る舞いの特徴を示しています.
- テリビウム (Tb) の同胞は14 Kの磁気ヒステレスと13.9 K (100 秒) のブロック温度を示しています.
- N(2)(3-) ラジカルブリッジは,磁気交換カップリングを効果的に媒介し,ゼロフィールドの緩和を妨げ,動作温度範囲を拡大します.
結論:
- Tb (III) アニソトロピーとN (II) (III) 基交換結合の相乗効果の組み合わせにより,これまでに報告された中で最も硬い分子磁石が得られる.
- ラジカルブリッジは,より高い温度で強固なゆっくりとした磁気放松を達成するために不可欠です.
- これらの発見は,性能を改善した高度な分子磁性材料を設計するための道を開く.
関連する概念動画
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.
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...
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
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...
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...
01:05Atomic Nuclei: Magnetic Resonance
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...