Rare-Earth and Iron Magnetism Duke It Out in a High-Temperature Superconductor

Scientists have observed for the first-time changes in magnetic order that point to an important interplay between rare-earth and iron magnetism in rare-earth iron arsenide superconductors. Magnetism is believed to play a key role in causing superconductivity in this class of high-temperature superconductors. Large single crystals and x-ray and neutron techniques in combination with magnetization and electric transport measurements enabled this discovery. Researchers have found that the iron atoms in neodymium iron arsenide are antiferromagnetically ordered along two crystallographic directions, meaning the magnetic moments are aligned in opposite directions from atom-to-atom. In the third dimension, the moments are ferromagnetically aligned, meaning in the same direction. However, as temperature decreases, the neodymium moments also start to order and cause the iron magnetic moments to realign from antiferromagnetic to ferromagnetic in one of the directions. This effect was not visible using powder specimens. This change in the iron magnetic order points to a delicate balance of magnetic interactions in this class of superconductors and is key to understanding their intriguing properties.

Contact: L. A. Lograsso, lograsso@ameslab.gov

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