Shrinking Superconducting Crystal
There is always a way to surprise someone. Researchers at NIST and the University of Maryland were quite surprised when working with an iron superconductor. Many high-temperature superconductors use copper, but some use iron instead, with some advantages and disadvantages. The iron superconductors can be manipulated to express certain properties, by changing the atoms in the crystal structure of the material. However, they do not have as high a limit of superconductivity. The researchers did manage to achieve a new record though, by reaching 47 K before superconductivity was lost.
The surprise involves how they reached this new temperature. The iron superconductor is of the 1:2:2 class, which refers to its crystal having one calcium atom at the center, with two iron and two arsenic atoms connected to it. The researchers removed the calcium atom to replace it with a smaller atom; this lead to the higher temperature. It also caused the crystal to collapse by 10%. That is a very dramatic size change and quite noticeable on scans. The researchers have found a way to prevent this collapse from happening, without sacrificing superconducting, which is important as a manufacturer could not use something that suddenly shrinks when being used.