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Atomic Nuclei: Nuclear Relaxation Processes

Atomic 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.

Atomic Nuclei: Nuclear Spin State Overview

Atomic Nuclei: Nuclear Spin State Overview

NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...

Atomic Nuclei: Types of Nuclear Relaxation

Atomic Nuclei: Types of Nuclear Relaxation

Nuclear relaxation restores the equilibrium population imbalance and can occur via spin–lattice or spin–spin mechanisms, which are first-order exponential decay processes.
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...

Atomic Nuclei: Nuclear Spin State Population Distribution

Atomic 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.

Ferromagnetism

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...

The Quantum-Mechanical Model of an Atom

The Quantum-Mechanical Model of an Atom

Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of a particle moving in quantized circular orbits, Erwin Schrödinger extended de Broglie’s work by deriving what is now known as the Schrödinger equation. When Schrödinger applied his equation to hydrogen-like atoms, he was able to reproduce Bohr’s expression for the energy and, thus, the Rydberg formula governing hydrogen spectra.

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Updated: Feb 25, 2026

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Published on: March 24, 2019

原子的に薄い反鉄磁石の6つの状態の時計物理.

Frank Y Gao¹, Dong Seob Kim¹, Chao Lei¹

¹Department of Physics and Center for Complex Quantum Systems, The University of Texas at Austin, Austin, TX, USA.

Nature materials

|February 23, 2026

まとめ

この要約は機械生成です。

研究者はNiPS3の2D XYモデルを研究し,3Dから2DのBerezinskii-Kosterlitz-Thouless (BKT) 状態への磁気行動移行を単層で発見しました. このBKT相は低温で不安定になり,長距離の秩序ある状態を形成します.

さらに関連する動画

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Published on: May 3, 2019

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

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

Published on: June 7, 2018

関連する実験動画

Last Updated: Feb 25, 2026

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Visualizing Uniaxial-strain Manipulation of Antiferromagnetic Domains in Fe1+YTe Using a Spin-polarized Scanning Tunneling Microscope

Published on: March 24, 2019

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Preparing an Isotopically Pure 229Th Ion Beam for Studies of 229mTh

Published on: May 3, 2019

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

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

Published on: June 7, 2018

科学分野:

凝縮物質物理学凝縮物質物理学
量子材料は,量子的な物質である.
スピントロニクス (Spintronics) は,スピントロニクス (Spintronics) を開発したものです.

背景:

量子物質の集合的行動と相変遷は,対称性の破裂とトポロジーによって支配される.
2D XY モデルは,準遠距離順序を理解するために不可欠な Berezinskii-Kosterlitz-Thouless (BKT) 移行を示しています.
アニゾトロピー場はBKT相を不安定化し,低温で真の長距離秩序をもたらす.

研究の目的:

ヴァン・デル・ワールズの反鉄磁石NiPS3.3におけるBKT移行とトポロジカルダイナミクスを研究する.
NiPS3を単層に薄めることで,3Dから2Dの磁気行動への移行を調査します.
2DBKT相の安定性と低温での変換を検証する.

主な方法:

非線形光学マイクロポリメトリを使用して,磁気特性を探査しました.
NiPS3を単層に薄めるとの磁気反応を調査した.
実験結果を裏付けるためにモンテカルロシミュレーションを行った.

主要な成果:

マルチレイヤーの3D XXZの振る舞いから2D BKTのような状態への突然のスイッチが単層のNiPS3.3で観察されました.
単層BKT相は,さらに冷却すると不安定になる.
低温で長距離順序を持つピン状態への変換を特定しました.

結論:

モノレイヤのNiPS3は,BKT状態を示しており,これは不安定であり,低温で長距離順序に移行する.
この研究は,2D反鉄磁石におけるトポロジカルダイナミクスとスピン渦に関する洞察を提供します.
この結果は,量子材料におけるトポロジカル・フェーズ・トランジションの探索に新たな道を開く.