Magnetic Moment of a Rare-Earth Magnet?

In summary, the equation for finding the magnetic field at a distance x from a rare-earth magnet is B=\mu_o*2\mu/(4\pi*d^3). To approximate the magnetic moment, \mu, for a neodymium magnet, you can multiply its volume by the value of 875kA/m. However, this approximation may not be accurate for AlNiCo or iron magnets due to their different permeability, but it may hold true for ferrite magnets.
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I was trying to find the value of the magnetic field at a distance x from a rare-earth magnet and came across this equation:

[itex]B=\mu_o*2\mu/(4\pi*d^3)[/itex]

Does anyone happen to know the magnetic moment, [itex]\mu[/itex], of a rare-earth magnet? Nothing specific, an order of magnitude value is fine.

Thank you!
 
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  • #2
For a neodymium magnet that has permeability near 1 and produces around 1.1T in short-circuit, you could:
multiply its volume by 1.1T/(4pi*10-7)
that is, volume * 875kA/m.

With neodymium, this approximation is not bad. True data there for instance:
http://www.cy-magnetics.com/CY-Mag-NdFeB.pdf
remember 1 G = 100 µT and 1 Oe produces 1 G in vacuum. These were the CGS units.

AlNiCo magnets, as well as iron magnets, have an important permeability, so you can't convert their short-circuit induction to the coercivity as if they were vacuum plus a coil. But with ferrite magnets, the approximation holds more or less.
 

FAQ: Magnetic Moment of a Rare-Earth Magnet?

What is the magnetic moment of a rare-earth magnet?

The magnetic moment of a rare-earth magnet is a measure of its strength and direction of magnetization. It is a vector quantity and is typically expressed in units of Tesla meters squared (Tm^2) or Ampere meters squared (Am^2).

How is the magnetic moment of a rare-earth magnet determined?

The magnetic moment of a rare-earth magnet is determined by its composition, shape, and size. It is also affected by external factors such as temperature and magnetic fields. The magnetic moment can be measured using specialized equipment, such as a vibrating sample magnetometer.

What makes rare-earth magnets have a high magnetic moment?

Rare-earth magnets, also known as neodymium magnets, have a high magnetic moment due to their unique atomic structure. They are made from alloys of rare-earth elements and iron, which have high magnetic moments themselves. This combination results in a strong and permanent magnet.

Can the magnetic moment of a rare-earth magnet be changed?

The magnetic moment of a rare-earth magnet is a fundamental property and cannot be changed. However, its strength can be affected by external factors such as temperature and magnetic fields. Exposure to high temperatures can cause a permanent decrease in the magnetic moment of the magnet.

What are the applications of rare-earth magnets based on their magnetic moment?

Rare-earth magnets have a high magnetic moment, making them useful in a wide range of applications. They are commonly used in motors, generators, speakers, hard disk drives, and magnetic resonance imaging (MRI) machines. Their strong magnetic moment also makes them popular in magnetic levitation experiments and as fasteners in industrial settings.

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