# Magnetization of a gas

1. Mar 24, 2014

### bobie

What happens if we apply a magnetic field to a gas in vacuum, (like H or He)?,
do the atoms get aligned like in ferromagnetic material and produce in their turn a strong magnetic field?,
if they don't, why so?

Thanks

2. Mar 24, 2014

### PhysicoRaj

It depends on which gas it is. Most of the gases are diamagnetic, some paramagnetic and ferromagnetic gases are very rare.

3. Mar 24, 2014

### bobie

Can you give me an example of ferromagnetic gas? and what about H?
Since in a gas atoms are not bound (as in iron) what determines its reaction to a magnetic field?

Last edited: Mar 24, 2014
4. Mar 24, 2014

### UltrafastPED

5. Mar 24, 2014

### bobie

Thanks for the interesting ling, Ultrafast, If I got it right alignment can occur at extremely low temperatures, because repulsive collisions between atoms are stronger than the magnetic force, and I suppose in laboratoty you cannot get a sufficiently strong magnetic field.

I hope you could explain a couple o obscure points
in your wiki article they say "The permanent moment generally is due to the spin of unpaired electrons in atomic or molecular electron orbitals (see Magnetic moment). "
- is the magnetism dependent only on the electron spin (which is very weak : $\hbar$?
doesn't the B field produced by the standing wave ,which is a lot stronger, play any tole at all?
- In QM, I learned, the electron wave id 3-D, how can the electron spin be stuck only in one direction
in such model?
Thanks

Last edited: Mar 24, 2014
6. Mar 24, 2014

### UltrafastPED

Electron spin - the Pauli exclusion principle permits two electrons in the same "quantum state" = "orbital" if they have opposite spin.

The spin of an electron has an associated magnetic moment - thus the unpaired electrons are the most important source for magnetic fields at the atomic/molecular level.

7. Mar 25, 2014

### bobie

Thanks, ultrafast, I am thinking of H to take the simplest case

I meant:
yes, the spin does have a magnetic moment, $\mu$(e)
- does it have also an associated magnetic field B(e)?, and,
- does the magnetic field generated by the orbit B(o) and its associated magnetic moment $\mu$(o) play any role in the magnetization ?
Thanks again

8. Mar 25, 2014

### UltrafastPED

9. Mar 30, 2014

### bobie

We know that in QM the value of the spin momentum L(e) and the value of the orbital momentum L(o)(http://en.wikipedia.org/wiki/Orbital_motion_(quantum)#Orbital_Angular_Momentum) are the same as in classical model = $\hbar$, the value of $\mu$e is $\hbar*2.0023$ (ge), right?

What is the value of B(e) and B(o) in neutral H atom according to QM model or current theory? how do we calculate it?