Ok, I was just curious but the electromagnetic force can allow paramagnetism macroscopically in some objects. Can this be done microscopically to the subatomic level? Also, what about other forces (besides gravity I'm guessing) meaning the weak and strong force? Strong force being the strongest, would its para- also be and always be stronger?


First, there is no universal inequality that would say that materials have to be "paramagnets". The opposite effects imply that materials may also be "diamagnets" which means that they react oppositely to the magnetic field. I think that atoms and molecules are the smallest objects whose response to the magnetic field may be viewed as the microscopic cause of diamagnetism and paramagnetism. It usually boils down to the electrons' motion but one couldn't analyze the magnetic behavior for the electrons in isolation.

Second, one can't talk about the reaction to uniform weak-magnetic and strong-magnetic fields because there aren't any. At least today, the electroweak symmetry is broken which means that the "weak-electromagnetic waves" are as short as the wavelength of the W-boson or Z-boson which is $10^{-18}$ meters or so; and they never quite move by the speed of light. No atom - and even no actual particle we know - may be squeezed to shorter distances or studied to shorter distances. This prevents us from talking about responses to uniform fields - simply because there are no uniform fields.

Analogously, the "strong electromagnetic fields" are non-uniform and variable because of a different reason in this case: the equations describing them are non-linear. There may be domains of size $10^{-15}$ meters or so where the "strong magnetic fields" may be aligned. See

Is the color gauge group spontaneously broken in QCD by the Savvidy vacuum?

But these domains are still too small to be studied as a uniform field in which other particles may peacefully inserted and analyzed. The strong and weak nuclear interactions create such a frantically changing environment that they're almost universally studied and described in terms of particle collisions. There are no peaceful macroscopic uniform fields; the latter is only possible for long-range forces such as electromagnetism and gravity.

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    $\begingroup$ There is the very weak but measurable paramagnetism from atomic cores (spin-paramagnetism). I'd call that "subatomic" $\endgroup$ – Georg Mar 4 '11 at 10:29

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