Re: Can ice become magnetic?

What an interesting question. Magnets are generally pretty mysterious since most of us really don't understand how they work, and what effects they have on other matter.

A science guy named Greg Goebel has posted a number of pages of information on a variety of subjects including physics and quantum mechanics. His page on quantum chemistry (http://www.vectorsite.net/tpqm_04.html) provides an extensive overview of the subject including how it relates to magnetism. Now, I spent some time in classes on quantum chemistry, but that was a long time ago and I don't know that I really understood most of what was being taught, but fortunately there are a lot of people brighter than I am.

After discussing the orbital properties of the atoms, about 3/4 of the way down the page, Greg gets to "3.4 MAGNETIC PROPERTIES OF THE ATOM." He goes on to explain "One of the subtle consequences of the electronic configurations of the different elements is their magnetic properties. A spinning electron has a magnetic moment, meaning it acts like a little bar magnet. When two electrons occupy the same orbital, they have opposed spins and so opposed magnetic moments, and their magnetic effect cancels out. However, if an element has orbitals with only one electron, the atom inherits a magnetic moment from the unpaired electrons."

He goes on to explain that atoms with a magnetic moment (an unpaired electron) can react in one of three ways with an external magnetic field. First, they can align themselves with the field, as illustrated by this figure:

When all the atoms align themselves with the external magnetic field, we refer to those materials as paramagnetic. The second way that materials can react is by not only aligning themselves with the external magnetic field, as with paramagnetic materials, but actually staying aligned after the magnetic field is removed, as illustrated by:

Such materials are called ferromagnetic. Iron is a good example of a ferromagnetic material; you put it near a strong magnetic field, and the iron will retain some magnetism after the field is removed. Ferromagnetic materials also have a "transition temperature," a temperature above which thermal movements basically start mixing up the atoms again, and destroy the magnetism that was remaining in the ferromagnetic material. So, above the transition temperature, ferromagnetic materials behave basically like paramagnetic materials.

Now most atoms with a magnetic moment that are neither ferromagnetic or paramagnetic are diamagnetic. Here is an illustration of how the atoms in a diamagnetic material react to an external magnetic field:

You will note that the magnetic domains are aligned in the opposite direction from the external magnetic field. What this means is that diamagnetic materials tend to move away from magnetic fields. Jay H. Hartley, a fellow mad scientist, provided an answer to the question Is Snow or Ice Magnetic? He points out both water and ice are diamagnetic, and provides links to a couple of interesting sites.

The fact that ice is diamagnetic can be demonstrated by hanging an ice cycle from a very thin string and then bringing a strong magnetic near one end of it. The ice cycle will twist away from the magnet.

So, with that background, let's see if we can answer your question. If you freeze water in a very strong magnetic field, you would expect the water molecules to align themselves opposite the direction of the magnetic field. By giving the water atoms a little more order than they would normally have, you might expect that it would be slightly easier to freeze the ice than without the magnetic field. In 2004, a group of Japanese researchers tried that experiment. By putting water in a 6 T magnetic field (the world record for a magnetic field is around 35 T) they were able to get the ice to freeze at 0.0056 C higher than the normal freezing point of 0 C. So the effect of a magnetic field on freezing temperature of ice is very, very small.

Diamagnetic materials (apparently) don't have a stable quantum state that allows the magnetic orientations to persist once the magnetic field is removed. Therefore, it doesn't appear that anyone has been able to freeze the magnetic structure in ice, once the external magnetic field is removed. Were it possible, it seems that the magnetic field produced by ice would be very weak.

So, I hope that answers your question.