Scientists discover a surprising quantum effect in cobalt-iron alloys often found in hard disk drives that might affect the storage of information.
The effect has something to do with the control of the direction of the electron spin. The findings could lead to the development of more powerful and more energy-efficient materials for storage of information.
Quantum Effects On Cobalt-Iron Alloy Materials
The researchers explained that the effect involves something called "damping" in which the electron spin direction influences how the material dissipates energy. Olle Heinonen, one of the authors of the study, compared the process to a car cruising down the highway.
"When you drive your car down a flat highway with no wind, the dissipating energy from drag is the same regardless of the direction you travel," said Heinonen who is a material scientist from the U.S. Department of Energy's Argonne National Laboratory. "With the effect we discovered, it's like your car experiences more drag if you're traveling north-south than if you're traveling east-west."
He explained that in their study, they found that magnetic damping has a sizable effect in nanoscale layers of cobalt-iron alloy. This comes as a surprise because the material has been in use in magnetic hard drives for decades. It is common knowledge that the material does not have a preference on electron spin direction and magnetization.
However, the researchers continued that in the past, scientists prepared the alloy by baking it at high temperature. The process arranges the cobalt and iron atoms into a regular lattice that eliminates directional effects.
For unbaked cobalt-iron alloys, the cobalt and iron atoms do not follow the same arrangement. Instead, the cobalt and iron atoms sat on each other's spaces.
"In a crystal structure, atoms normally sit at perfectly regular intervals in a symmetric arrangement," the press release reads. "In the crystal structure of certain alloys, there are slight differences in the separation between atoms that can be removed through the baking process; these differences remain in an unbaked material."
Squeezing the material in an atomic level changes the separation of the atoms even more, leading to different interactions between atomic spins in the crystalline environment. This is why the damping effect on magnetization changes with the direction of the electron spin.
Magnetizations Could Herald Improvement In Information Storage
The researchers believe that their findings that appear in the journal Physical Review Letters could lead to the development of better materials for hard disk drives. Gaining control of the electron spin direction of a material and, therefore, magnetization could enable information to be stored and accessed from a smaller space.
The findings could also be applied to other fields, including the development of more energy-efficient electric motors, magnetic bearings, and generators.