Dancing With Electrons

By Roland Piquepaille

You'll find there articles on manufacturing process design, semiconductor design and production, design of new materials, and aerospace engineering.

I selected one article for you, about magnetic properties of thin films.

Dancing and magnetism are fundamentally comparable, according to physicist Arthur Freeman of Northwestern University.

In the three-dimensional dance space occupied by an atom, electrons pair up as they revolve around the nucleus, each spinning on its axis in an opposite direction to its partner -- in effect, canceling each other's spin. Among the outermost electrons of some metal atoms, however -- those most weakly bound to the nucleus, a few unpaired electrons spin in the same direction. It's this net unpaired spin, explains physicist Freeman of Northwestern University, that in these magnetic metals gives rise to a "magnetic moment," creating the pull of a magnetic field.

Nice words, but what can we expect from this?

Relying on powerful computational methods at PSC to simulate the bewildering complexity of this atomic dance floor, Freeman has revolutionized ideas about magnetism. During the last decade he has shown, contrary to what physicists believed prior to his work, that a surface atomic layer of a metal can have more magnetic moment than the bulk form of the same metal. Research stimulated by this finding has led to increasing magnetic data storage on compact discs by more than 40 times.

Here is an illustration from Freeman's work, which shows a calculated electron spin density for the surface of iron (left) compared to the free monolayer (right). Dark blue indicates negative spin, and other colors are positive, increasing from light blue through pink.

It is interesting to note that Freeman's research was done on a Cray C-90 supercomputer.

Source: Pittsburgh Supercomputing Center