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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...

Ferromagnetism

Ferromagnetism

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Atomic Nuclei: Nuclear Magnetic Moment

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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...

Atomic Nuclei: Nuclear Spin State Population Distribution

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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.

Diamagnetism

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.
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Atomic Nuclei: Nuclear Relaxation Processes

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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.

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Related Experiment Video

Updated: Aug 2, 2025

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

Terahertz Spin Current Dynamics in Antiferromagnetic Hematite.

Hongsong Qiu¹, Tom S Seifert², Lin Huang³

¹Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing, 210023, P. R. China.

Advanced Science (Weinheim, Baden-Wurttemberg, Germany)

|April 21, 2023

Summary

Hematite (α-Fe2O3) generates terahertz spin currents using ultrafast laser pulses. Researchers controlled these spin currents, paving the way for advanced spintronic devices.

Keywords:

antiferromagnets spin currents spin dynamics terahertz spectroscopy

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Last Updated: Aug 2, 2025

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

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Published on: March 24, 2019

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

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Published on: July 20, 2022

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Sputter Growth and Characterization of Metamagnetic B2-ordered FeRh Epilayers

Published on: October 5, 2013

Area of Science:

Condensed matter physics
Materials science
Spintronics

Background:

Antiferromagnets (AFMs) are crucial for next-generation spintronic devices.
Hematite (α-Fe2O3) exhibits Dzyaloshinskii-Moriya interaction, enabling coexisting antiferromagnetism and weak ferromagnetism.

Purpose of the Study:

To investigate the generation and control of terahertz (THz) spin currents from hematite.
To explore the dynamics of spin current generation in α-Fe2O3 for ultrafast spintronic applications.

Main Methods:

Utilizing femtosecond laser pulses to induce spin currents in hematite.
Employing terahertz (THz) spectroscopy to analyze spin current dynamics.
Applying magnetic fields up to 1 Tesla to manipulate spin current generation.

Main Results:

Demonstrated THz spin current generation from α-Fe2O3 into an adjacent platinum layer.
Identified two distinct spin current dynamics: impulsive stimulated Raman scattering (AFM order-dependent) and ultrafast spin Seebeck effect (net magnetization-dependent).
Showed that medium-strength magnetic fields (below 1 T) can effectively control the total THz spin current.

Conclusions:

Hematite serves as a viable material for generating ultrafast spin currents.
The distinct dynamics of spin current generation offer pathways for precise control.
This research advances the development of controllable ultrafast antiferromagnetic spin sources for spintronics.