Scientists from SLAC and Stanford have used finely tuned X-rays at the Stanford Synchrotron Radiation Lightsource (SSRL) to pin down the source of a mysterious magnetism that appears when two materials are sandwiched together.
Why is this mysterious?
Neither material shows a hint of magnetism on its own.
Both materials are perovskites, a class of mineral oxides whose unique electronic properties are of great interest to scientists. Perovskites already have a variety of industrial uses, and researchers are busy trying to find ways to transform some of them – such as the high-temperature superconductors – into materials that could transform our energy grid or help create environmentally friendly fuels.
These particular perovskites are known as LAO (lanthanum aluminum oxide) and STO (strontium titanium oxide), and both are insulators. But when sandwiched together, the resulting “heterostructure” can conduct electricity at the interface where the materials meet. In fact, when cooled to near-absolute zero this heterostructure becomes a superconductor, conducting electricity without any resistance. Even more puzzling, it displays magnetic qualities at the juncture where LAO and STO meet – something neither material does alone, even when doped with impurities to tune its properties.
Which particular atoms acquire this new property? That’s what the researchers wanted to learn, and the results of their study appeared this week in Nature Materials.
The researchers studied sample heterostructures, each one an extremely thin layer of LAO on an STO substrate. The samples were grown by the group of Harold Hwang of the Stanford Institute for Materials and Energy Sciences (SIMES), a joint SLAC-Stanford institute. Hwang is an expert in this heterostructure; he’s been studying it for a decade.
Read more at: Phys.org