Deep inside rocky planets like Earth, the behavior of iron can greatly affect the properties of molten rock materials: properties that influenced how Earth formed and evolved.
In fact, the evolution of our entire planet may be driven by the microscopic quantum state of these iron atoms. One special feature of iron is its “spin state,” which is a quantum property of the electrons in each iron atom that drives their magnetic behavior and reactivity in chemical reactions. Changes in the spin state can influence whether iron prefers to be in the molten rock or in solid form and how well the molten rock conducts electricity.
Until now, it’s been challenging to recreate the extreme conditions in these molten rock materials, called silicate melts, to measure the spin state of iron. Using powerful lasers and ultrafast X-rays, an international team of researchers at the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University, Universite ́ Grenoble Alpes, Laboratoire pour l’Utilisation des Lasers Intenses (LULI), and Arizona State University overcame this challenge. They showed that at extremely high pressures and temperatures, the iron in silicate melts mostly has a low-spin state, meaning its electrons stay closer to the center and pair up in their energy levels, making the iron less magnetic and more stable.