Mu metals

[5614]

I was wondering how mu metals (aka [math]\mu[/math] metals) work?

 

I mean, for example, an antiferromagnetic material has domains which are aligned in a regular pattern whereby each domain is pointing in the opposite direction to the on either side, so it'd be like up, down, up, down etc.

 

How are the domains aligned in [math]\mu[/math] metals that allow them to have their magnetic field absorption or blocking effect.

 

I assume it is different from antiferromagnetic materials because it's a different name!

[5614]

Well thanks for all the help!!!

 

I think it's to do with the fact that [math]\mu[/math] metals have high magnetic permiability.

 

So there will exist a magnetic field on the other side, it'd just be very weak.

 

The symbol for magnetic permeability is [math]\mu[/math], hence the name [math]\mu[/math] metals for metals which have a high magnetic permeability.

[quick silver]

hi. i'm glad that you figured out what the answers was.

 

iron, cobalt, nickel. is this not what our earth's core is made from?

[5614]

We do not know for certain what the earth's core is made out of.

 

Using the refraction patterns of seismic waves we can dedcude that it is a solid and using the refractive index we can get an approx idea of the density... but no, we do not know much, other than it is a solid.

 

And that was a bit kinda off topic! Back to [math]\mu[/maths] metals...

[quick silver]

ok...............metals........magnets.................

[swansont]

Well thanks for all the help!!!

 

I think it's to do with the fact that [math]\mu[/math] metals have high magnetic permiability.

 

So there will exist a magnetic field on the other side' date=' it'd just be very weak.

 

The symbol for magnetic permeability is [math']\mu[/math], hence the name [math]\mu[/math] metals for metals which have a high magnetic permeability.

 

Sorry - I didn't see this one first time around. You are absolutely right. The magnetic fields can be realigned by "degaussing" the material - you subject it to a strong, oscillating field, which kind of scramble the domains, and then you turn the degaussing field off slowly, so that the external field is all that's left. That way you don't get a different bias field in place.

 

Here is the magnetic field model of a set of four magnetic shields made from one manufacterer's recipe for mu-metal.

[5614]

That link is from where you work!!! (I recognised it!)

 

So can you just explain how mu metal's domains work...

 

Is it like they are randomly aligned, then when a manget is brought near it they will align but because they have high magnetic permiability not much of the magnetic field can go through it? Be induced into it? Or what?

 

Also what, on an atomic or domain or electron kind of scale makes a metal have high (or low) magnetic permiability?

[swansont]

That link is from where you work!!! (I recognised it!)

 

So can you just explain how mu metal's domains work...

 

Is it like they are randomly aligned' date=' then when a manget is brought near it they will align but because they have high magnetic permiability not much of the magnetic field can go through it? Be induced into it? Or what?

 

Also what, on an atomic or domain or electron kind of scale makes a metal have high (or low) magnetic permiability?[/quote']

 

These might help:

 

MuShield FAQ

 

Magnetic Shield Corp FAQ

[5614]

Thanks for the links, the 1st one was very good, the 2nd was more general and less what I wanted.... but thanks!

 

These two questions still stand though:

 

1) Mu metal domains: Is it like they are randomly aligned, then when a manget is brought near it they will align but because they have high magnetic permiability not much of the magnetic field can go through it? Be induced into it? Or what?

 

2) Permiability: Also what, on an atomic or domain or electron kind of scale makes a metal have high (or low) magnetic permiability?

[swansont]

Thanks for the links' date=' the 1st one was very good, the 2nd was more general and less what I wanted.... but thanks!

 

These two questions still stand though:

 

[b']1)[/b] Mu metal domains: Is it like they are randomly aligned, then when a manget is brought near it they will align but because they have high magnetic permiability not much of the magnetic field can go through it? Be induced into it? Or what?

 

2) Permiability: Also what, on an atomic or domain or electron kind of scale makes a metal have high (or low) magnetic permiability?

 

Permeability is going to relate to how easily you can align the domains. The domains arise because there is a mechanical structure to the material (some kind of lattice) and the individual atoms have unpaired electron spins whose fields have a fixed alignement to the atom.

 

The domains will align to whatever field they are in, if it's strong enough to reorient them, or the material is heated and then cooled properly. You hear a buzzing when you degauss them, because the orientation has slightly different physical length of the domains, so if you but a 60 Hz field nearby, the metal will expand and contract ever so slightly at 60 Hz as the domains reorient themselves. (You can sometimes hear this in a transformer on an overhead power line as well. This effect is called magnetostriction). But I don't think the domains can take any orientation - that's fixed somewhat by the physical structure. What I think is happening is that you created various domains, and they can then have two different orientations when you flip the spin of the electron. So they will align as best they can with an external field. A high permeability means there are lots of atoms/domains that can line up easily.