シングルチェーン磁石に対する傾いた反鉄磁気アプローチ
Kevin Bernot1, Javier Luzon, Roberta Sessoli
1INSTM Research Unit-Dipartimento di Chimica, Università di Firenze, via della Lastruccia 3, 50019 Sesto Fiorentino, Firenze, Italy.
Journal of the American Chemical Society
|January 16, 2008
まとめ
この研究では,単一鎖磁石の振る舞いを示す新しい一次元マンガン (((III)) 化合物を合成しました. この材料は,傾斜した反鉄磁気配列と,単鎖磁石の特徴であるダイナミックな磁気特性を示しています.
科学分野:
- 無機化学 無機化学とは
- 材料科学 材料科学とは
- マグネチズム (磁気) とは
背景:
- ポルフィリンリガンドを含むマンガネス (III) 複合体は,その磁性特性に注目されています.
- 一次元の協調ポリマーは,ユニークな磁気行動を提供します.
- 構造-性質の関係を理解することは,新しい磁気材料の設計に不可欠です.
研究 の 目的:
- 新しい一次元マンガン (III) 化合物を合成し,特徴づけること.
- 静的および動的行動を含む磁気特性を調査する.
- 観測された磁気現象と化合物の結晶構造を相関させるため.
主な方法:
- [Mn(TPP) O2PHPh] x H2Oの合成,マンガネス(III) アセテートメソテトラフェニルポルフィリンとフェニルフォスフィン酸の反応による.
- 単結晶X線 difraktionで結晶構造を決定する (モノクリニックC2/c).
- 単一結晶の静的および動的磁気感受性測定.
- 磁気パラメータを分析するための古典的なモンテカルロシミュレーション.
- アレニウスの法則を用いたリラックスダイナミクスの分析.
主要な成果:
- 化合物は,1次元鎖構造を形成し,Jahn-Tellerの長方形のMn (III) 八面体が交互に交差しています.
- 有意な反鉄磁気交換相互作用 (J = -0.68(4) K) と簡単な軸アニソトロピー (D = -4.7(2) K) が決定されました.
- 5K以下では,周波数依存のアウト・オブ・フェーズ信号が単鎖磁石の振る舞いを示した.
- リラクゼーション時間はアレニウスの法則 (デルタ=36.8K) に従い,特徴的な長さは感受性による推定相関長さを上回る.
結論:
- フェニルフォスフィナートアニオンは強力な反鉄磁気交換を媒介し,反鉄磁気回転配列の傾斜につながります.
- この化合物は,単鎖磁石の特徴を示し,動態はエネルギー障壁によって支配されます.
- 観測された磁気動力は,構造的特徴,特に相関長さに強く影響されています.
関連する概念動画
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...
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.
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.
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...
Magnetic Fields
A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
A magnetic field is defined by the force that a charged particle experiences...
Atomic 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...
Atomic Nuclei: Nuclear Magnetic Moment
All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...


