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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
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Flipping Atoms in a Flash
13 May 1999 7:00 pm
Researchers have found a very fast way to flip the magnetic alignment of atoms in a layer of nickel and iron, using an ultrashort pulse of laser light. The finding, reported in the 3 May issue of Physical Review Letters, could be used in future generations of hard disks, which use magnetic orientation to store information.
A material becomes magnetic when most of its atoms--which behave like tiny magnets--point in the same direction. One way to flip the direction of atoms in a small region of the material to record a bit of information is to expose it to a magnetic field, created by running electricity through a tiny wire loop. But electricity can be sluggish, so it takes some time to get the atoms to move. "We thought there might be some way of circumventing that process using short pulses of light," says Arto Nurmikko, a physicist at Brown University in Providence, Rhode Island.
The trick was to create a material in which the laser could briefly unpin the atoms, enabling an external field to rapidly reverse their direction. Nurmikko and his colleagues used a slice of a material made up of layers of nickel iron at the bottom and nickel oxide on top. Nickel iron is ferromagnetic; an external magnetic field can align its atoms. Nickel oxide is antiferromagnetic: atoms in adjoining layers point in opposite directions. But the interaction of the two materials at their interface creates an internal magnetic field that aligns all the atoms in the nickel iron layers. Because nickel oxide is transparent, the researchers could shoot a laser pulse lasting just a trillionth of a second through it to reach the top nickel iron layer. The pulse shook up the electrons in this layer, freeing the atoms from the internal field. Once this happened, the atoms in the nickel iron layer could flip direction in response to another magnetic field that the researchers had applied from the outside. Their magnetization reversed in just 10 billionths of a second, more than 10 times faster than in a conventional disk drive.
"This is an extremely clever experiment," says William Doyle, a physicist at the University of Alabama, Tuscaloosa. But whether the method will ever make it into computers is debatable, says Marcos Lederman, a storage technologist at Read Rite, a company in Fremont, California. The use of lasers and the complexity of the material may make the technology too expensive to be viable, he says.