Work on magnets

I don't study magnets. In fact, I don't know much about magnets beyond what I learned in undergraduate level physics. However, one of the things that I do remember is that scientists (at that time at least) didn't really know why magnetism worked; they merely knew some of the how.

Well, in my PhysOrg newsfeed this morning, I saw two stories about magnets.

In the first story, researchers de-magnetized a magnet in order to see how magnets worked, and - possibly - to make smaller magnets. Kinda cool.

In the material studied at EPFL, the atoms are arranged in pairs in a very particular way: the magnetic field of one atom is the opposite of that of its neighbor. As a result, the total magnetic field of each pair is practically nil. The entire material thus loses its magnetization.

To unveil the secrets of this strange magnet, the scientists bombarded a lithium-erbium-fluoride sample with neutrons. The radiation allowed them to measure the structure of the crystalline network and its magnetic properties at very high resolution. The experiment had to be conducted at very low temperatures in order to prevent the atoms’ Brownian motion from obscuring the results.

[W]hen they measured the magnetic properties of their sample, the physicists obtained an unexpected result. In this experiment, even though the sample was much thicker, it had the magnetic properties of a single layer.

Why is this cool? Well, because of miniaturization of hard disks:

Data are stored in binary form by changing the magnetic polarity of an area of the disk. With miniaturization, however, the problem is that sectors close to one another can influence each other, and spontaneously change polarity. The data would then be lost. “With these special materials, miniaturization could continue; each sector of the disk could be one of these magnetization-free pairs. The probability that the magnetic field of one atom would influence the magnetic field of its neighbor is practically nil.”

But that's still years off. Still, here's a pretty cool story that points to a the HDD analogue of Moore's Law being allowed to continue onward.

The next story is about how magnetism works in Helium-3 thin films (yeah, who knew such a thing existed?):

Thin films of helium atoms with nuclei of two protons and one neutron—helium-3—intrigue physicists because they have exhibited unusual and unexpected magnetic behavior in experimental investigations. ... The [researchers'] model also predicts the appearance of a new quantum state in solid helium-3 films. [The researchers] focused on solid-state helium-3 because it enabled them to study a phenomenon known as frustration. Helium-3 thin films are ‘frustrated’ by interactions between localized areas of magnetism known as spins. The atoms in these films are organized into a triangular lattice, so the interaction between nearest-neighbor-pairs requires that spins act in the same direction—a mechanism known as ferromagnetism. At the same time however, exchange interactions between multiple spins are antiferromagnetic; that is, alternating spins act in opposite directions. ... They found a previously unknown ground state that has a so-called octahedral spin nematic order; that is, the spins are arranged such that they point along a particular direction, and these ‘directors’ are orthogonal to each other.

Much of the brief runs over my head, but there is something between these two papers that I think is additionally cool: they both potentially describe the same underlying phenomenon! In the first brief, we read the following observation:

But when they measured the magnetic properties of their sample, the physicists obtained an unexpected result. In this experiment, even though the sample was much thicker, it had the magnetic properties of a single layer.

and in the second paper:

the spins are arranged such that they point along a particular direction, and these ‘directors’ are orthogonal to each other. Momoi and colleagues believe that it is this unusual arrangement that causes the anomalous magnetic behavior of two-dimensional solid helium-3.

They both are stories that try to explain how effectively 2-dimensional magnetic fields are formed.

Yeah, I know that it's kinda nerdy that I find all this interesting, even though magnetism isn't part of my research, but there you go. Too, I admit that I may well be wrong about my reading of the two papers - and maybe the whole 2-D magnetic field thing was already known, but I still think that it's cool, because it wasn't known at least to me.