Antiferromagnetic images seen in solids |
|
Researchers from Bell Labs, NEC Research Institute and Argonne’s Advanced Photon Source (APS) captured the first image of antiferromagnetism within a solid material. The technique they used could point the way to new advanced magnetic recording materials and technologies. In contrast to familiar magnets such as iron, antiferromagnets are difficult to identify. Just like ferromagnets, antiferromagnets contain magnetic atoms, each of which possesses a strong magnetic field. Antiferromagnets are “anti” because the fields for neighboring atoms align in opposite directions. The result is that an outside observer measures zero net field, which makes it difficult to detect antiferromagnets. To develop new technologies, researchers want to map the antiferromagnetic properties of materials. The team used the APS X-rays to watch changes in chromium, the most common metal in which antiferromagnetism is observed, as it was cooled below room temperature. “This research has extended the capabilities of the APS in a way that other disciplines can take advantage of as well,” said researcher Eric Isaacs of Bell Labs, part of Lucent Technologies. “We used the Advanced Photon Source to build an X-ray microscope, allowing us to look inside materials at dimensions below one micron.” A micron is a millionth of a meter. The researchers captured images of the magnetic activity in a single crystal of chromium. “Visualizing the organization of atoms and molecules in solids allows scientists to learn more about the possibilities of the materials,” Isaacs said. “The physics and chemistry of submicron devices need to be understood to take full advantage of their potential. These are crucial building blocks for technology.” “Historically, there have been few practical applications of antiferromagnets, because until now they have been extremely difficult to image,” added Gabriel Aeppli, senior research scientist at NEC Research Institute. “The new microscope makes it dramatically easier to map out antiferromagnets and analyze their structures for practical purposes.” The researchers made X-rays of chromium's antiferromagnetic domains—regions in which the atomic magnetism lies along a particular direction. On cooling the chromium below minus 150 degree Celsius (minus 240 degrees Fahrenheit), new types of domains appear via growth from the walls between domains of a type already present at room temperature. Now the researchers want to learn how the walls affect the passage of electric current. Their results could lead to nanoscale devices for computing and communications. Funding was provided by NEC and Bell Labs. For more information, please contact Catherine Foster. |