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Related Concept Videos

Paramagnetism01:30

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...
Applications Of NMR In Biology01:25

Applications Of NMR In Biology

Nuclear magnetic resonance (NMR) spectroscopy is a very valuable analytical technique for researchers. It has been used for more than 50 years as an analytical tool. F. Bloch and E. Purcell formulated NMR in 1946 and won the 1952 Nobel Prize in Physics  for their work. Biological macromolecules such as proteins, nucleic acids, lipids, and organic molecules including pharmaceutical compounds, can be studied using this versatile tool that exploits the magnetic properties of certain nuclei.
The...
Diamagnetism01:26

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.
Ferromagnetism01:31

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...
NMR Spectroscopy: Spin–Spin Coupling01:08

NMR Spectroscopy: Spin–Spin Coupling

The spin state of an NMR-active nucleus can have a slight effect on its immediate electronic environment. This effect propagates through the intervening bonds and affects the electronic environments of NMR-active nuclei up to three bonds away; occasionally, even farther. This phenomenon is called spin–spin coupling or J-coupling. Coupling interactions are mutual and result in small changes in the absorption frequencies of both nuclei involved. While nuclei of the same element are involved in...
Atomic Nuclei: Magnetic Resonance01:05

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...

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Related Experiment Video

Updated: May 28, 2026

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters
09:43

Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters

Published on: August 22, 2014

Magnetic interactions between nanoparticles.

Steen Mørup1, Mikkel Fougt Hansen, Cathrine Frandsen

  • 1Department of Physics, Building 307; Technical University of Denmark; DK-2800 Kongens Lyngby; Denmark.

Beilstein Journal of Nanotechnology
|October 7, 2011
PubMed
Summary
This summary is machine-generated.

Interactions between magnetic nanoparticles create collective states, suppressing relaxation. This behavior in hematite and goethite nanoparticles is modeled effectively using mean field theory.

Keywords:
dipole interactionsexchange interactionsspin structuresuperferromagnetismsuperparamagnetic relaxation

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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

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Synthesis of Immunotargeted Magneto-plasmonic Nanoclusters
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Published on: August 22, 2014

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

Published on: June 9, 2016

Area of Science:

  • Condensed matter physics
  • Materials science
  • Nanotechnology

Background:

  • Isolated magnetic nanoparticles typically exhibit superparamagnetism.
  • Interactions can significantly alter the magnetic properties of nanoparticle systems.

Purpose of the Study:

  • To provide an overview of how inter-particle interactions influence magnetic nanoparticle properties.
  • To explain the emergence of collective magnetic states and suppressed relaxation.

Main Methods:

  • Review of theoretical concepts (magnetic dipole interactions, exchange interactions).
  • Analysis of experimental observations in hematite and goethite nanoparticle systems.
  • Application of mean field models to describe temperature dependence.

Main Results:

  • Strong magnetic dipole and exchange interactions lead to collective states resembling spin-glasses.
  • Superparamagnetic relaxation is suppressed in aggregated magnetic nanoparticles.
  • Mean field models accurately describe the temperature dependence of the order parameter.
  • Exchange interactions can cause sublattice magnetization rotation.

Conclusions:

  • Inter-particle interactions are crucial for understanding the macroscopic magnetic behavior of nanoparticle assemblies.
  • Collective phenomena in magnetic nanoparticles can be effectively modeled using established physical principles.