Electron spin and magnetic permeability

[wospin]

Well,
This is my first post, I used to read topics here, time to make one!

Consider we have an oscillating magnetic field acting on a paramagnetic material, would this cause the unpaired electrons to alter their spin with the same frequency ?
If so, would this affect the magnetic permeability ?
in other words would it affect EM waves propagating through this medium ?
And what are the equations describing this effect?

 

[Relena]

Magnetic permeability is not constant but rather changes with frequency, this is called complex permeability, it has some applications in electrical engineering.

as for the equations you can find here
http://en.wikipedia.org/wiki/Permeability_(electromagnetism )

I don't think that the spin will be altered by the same frequency, electrons tend to change their polarity rather than spin, i think spin is indeterminate in QM, so you'll be dealing with probabilistic functions, something that is not representable in classical electromagnetism.

 

[wospin]

So, if the frequency of the magnetic field oscillation is higher than microwave frequency, would this cause reflection ?