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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...

Potential Due to a Magnetized Object

Potential Due to a Magnetized Object

Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...

Magnetic Field due to Moving Charges

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...

Paramagnetism

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...

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.
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.

Magnetic Susceptibility and Permeability

Magnetic Susceptibility and Permeability

In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...

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Related Experiment Video

Updated: May 30, 2026

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

Published on: February 5, 2022

Magnetoviscous effect in a maghemite ferrofluid.

E Ghasemi¹, A Mirhabibi, M Edrissi

¹Institute of Color Science and Technology (ICST), 16688-14811 Tehran, Iran.

Journal of Nanoscience and Nanotechnology

|July 21, 2011

Summary

This study synthesized iron oxide ferrofluid, revealing maghemite as the primary magnetic phase. The ferrofluid exhibits concentration-dependent phase separation under high magnetic fields, with smaller particles contributing at increased field strengths.

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Stable Aqueous Suspensions of Manganese Ferrite Clusters with Tunable Nanoscale Dimension and Composition

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Published on: February 5, 2022

Magnetically Induced Rotating Rayleigh-Taylor Instability

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Published on: March 3, 2017

Area of Science:

Materials Science
Nanotechnology
Rheology

Background:

Ferrofluids are colloidal suspensions of magnetic nanoparticles.
Understanding their magnetorheological properties is crucial for applications.
Particle size and concentration significantly influence ferrofluid behavior.

Purpose of the Study:

To synthesize and characterize iron oxide ferrofluid.
To investigate the magnetorheological properties and magnetic field effects.
To study the influence of particle size and concentration on magnetoviscous effects.

Main Methods:

Co-precipitation synthesis of iron oxide nanoparticles.
Characterization via X-ray diffraction, TEM, EELS, and DLS.
Rheological measurements using a rotating rheometer under varying magnetic fields.

Main Results:

Maghemite identified as the dominant magnetic phase.
Magnetoviscous effect causes concentration-dependent phase separation at high magnetic fields.
Smaller nanoparticles enhance performance at higher magnetic field strengths.

Conclusions:

The synthesized iron oxide ferrofluid exhibits tunable magnetorheological properties.
Particle size and concentration are key factors in controlling phase separation and viscosity.
Potential for tailored ferrofluid applications based on magnetic field response.