Magnetite is a rock mineral that takes three atoms of iron for every four of oxygen to form. It is one of the main iron ores and is the most magnetic of all the naturally-occurring minerals on Earth. Today it is mined as iron ore.
Gregory Fiete is a professor of Physics at Northeastern University. He, along with Martin Rodriguez-Vega, a postdoctoral researcher, has teamed up with a global group of collaborators to learn about the inner workings of magnetite. Magnetite has such physical properties that its material loses its ability to conduct electricity when it is cooled to 125 K. At that temperature, the material turns from being a metal, which transports charge, into an insulator, which doesn’t. Scientists have been trying to understand the mechanisms within magnetite’s atoms that lead to this elusive transition into the insulation. Magnetite crystals were shot with lasers by the team. They watched the behavior of the crystals closely as the laser’s light particles stimulated the atoms. They observed new ways in which magnetite’s electrons respond to the lasers. Those excitations indicate how magnetite’s electrons, and the way they arrange in the crystal’s structure, change as they turn the material into an insulator.
The findings have been published in Nature Physics as it is a result of a modern technique that first blasts a material with a laser to excite it and then uses a second, lower-energy laser, to probe its response at ultra-fast speeds of trillionths of a second. The researchers observed specific oscillations in the patterns of trimerons. These are basic units consisting of three iron ions which are aligned symmetrically within the structure of magnetite. These oscillations were accompanied by changes to the fundamental interactions of their electrons. These new findings are pushing the limits of what can be done in the lab- based on theoretical knowledge. Because the properties of magnets are essential for generating electricity, completing the puzzle of magnetite’s hidden powers could eventually lead to new ways to manipulate materials and improving electronics by harnessing the behaviour of their electrons.
Shahjadi Jemim Rahman