Researchers from Bell Labs, NEC Research Institute, Inc. and Argonne National Laboratory have created an image of antiferromagnetism within a solid material, using a new technique that could lead to more cost-efficient evolution of advanced magnetic recording materials and technologies.
Complete results of the research are published today in Science magazine.
In contrast to familiar magnets such as iron, antiferromagnets are reportedly difficult to identify. Just like ferromagnets, antiferromagnets contain magnetic atoms, each of which possesses a strong magnetic field.
In contrast to ferromagnets, however, they are ‘anti,’ because the fields for neighbouring atoms align in opposite, rather than the same, directions. The result is that an outside observer measures zero net field, which makes it difficult to detect antiferromagnets in the same way as scientists do ferromagnets – namely by observing attraction or repulsion by another ferromagnet.
Because of new technological interest in antiferromagnets, there is now a greater awareness of the importance of mapping their antiferromagnetic properties.
The researchers used Argonne’s Advanced Photon Source, America’s most efficient source of X-rays, to watch changes in chromium, the most common metal in which antiferromagnetism is observed, as it is cooled below room temperature.
‘Historically, there have been very few practical applications of antiferromagnets, because until now they have been extremely difficult to image,’ said Gabriel Aeppli, senior research scientist at NEC Research Institute. ‘The new microscope makes it dramatically easier to map out antiferromagnets and analyse their structures for practical purposes,’ he added.
The researchers made X-ray images of chromium’s antiferromagnetic domains- regions in which the atomic magnetism lies along a particular direction. On cooling the chromium below -150 C (-240 F) new types of domains appear via growth from the walls between domains of a type already present at room temperature.
The researchers now want to learn how the walls affect the passage of electric current, with the goal of inventing new types of nanoscale devices for computing and communications.