It's a strange scientific phenomenon: ultra-thin magnets are solid, but when zapped with lasers, they actually behave like fluids.
This fact has been known by academics for years. When an ultra-thin magnet is hit with a laser, it suddenly demagnetizes. Imagine tiny refrigerator magnets plopping on the ground. How does that happen?
In a new study, researchers from the University of Colorado Boulder are examining how magnets recover from this demagnetization and return to their original properties in a fraction of a second.
The implications of the study can have a huge contribution to computer engineering, particularly on computer hard drives, scientists said.
How Lasers Make Zapped Magnets Become Fluid-Like
There is a specific order to how the particles of magnets are formed, and materials with magnetic properties usually feature subatomic building blocks that all spin in the same direction, whether it be up or down. Earth's magnetic field works the same way.
However, a brief laser blast can disrupt this order. The magnetic properties begin to turn into "droplets," which is similar to what happens when a jar of oil and water is shaken up.
The team from the University of Colorado Boulder, which was led by Ezio Iacocca and Mark Hoefer, drew on mathematical modeling as well as numerical simulations and experiments that were conducted at the SLAC National Accelerator Laboratory in Stanford University to find the answers to their questions.
"What we were interested in is what happens after you blast it," said Iacocca. "How does it recover?"
Iacocca and his colleagues focused on a short but critical point in the life of a magnet: the first 20 trillionths of a second after a magnetic, metallic alloy gets hit by a short, high-energy laser.
Once hit with enough laser pulse, the "spins" or orientation of the magnet will no longer point just up or down, but in all different directions.
This cancels out the magnetic properties for 3 picoseconds, and then the magnet is back at equilibrium after a microsecond, explained Iacocca.
In Between Demagnetization, Something Happens
The researchers wanted to figure out what happens in that missing window of time, and to do that, they ran a series of experiments in California.
Iacocca and his colleagues blasted tiny pieces of gadolinium-iron-cobalt alloys with lasers. Afterward, they compared the results to computer simulations and mathematical predictions.
Hoefer, who is an associate professor of applied math, explained that the metals themselves do not turn liquid. Instead, the spins or building blocks within the magnets become fluid-like, and they move around and change their orientation likes waves in an ocean.
After a while, the disordered spins begin to settle down and then form small clusters with the same orientation. These "droplets" would then grow bigger and bigger, hence the comparison to oil and water that separates in a jar, Hoefer said.
Implications Of The Study
A zapped magnet does not always return to its original orientation, however. In some cases, Hoefer said a magnet can flip after being hit by a laser pulse, and then switch from up to down.
Researchers believe that when magnets flip from up to down, it can be used for computer engineering. In fact, the flipping can store information on a computer hard drive in bits of ones and zeros.
Iacocca believes if the flipping can be done more efficiently, it can even be used to build faster computers. He and his colleagues are in the process of understanding the flipping behavior more accurately so that they can find a magnet material that flips faster.
Details of the study have been published in the journal Nature Communications.
Photo: Douglas Muth | Flickr
