Houston (TX) - Magnetite, the ancient magnetic mineral called Lodestone, first documented over 2,000 years ago, and first used in primitive compasses by the Chinese 900 years ago, exhibits some interesting properties when it is cooled to around -250F. Magnetite is normally an electrical conductor. At around -250F it switches to an electrical insulator. This property was discovered about 60 years ago, but what was not known until recently was that if you apply a sufficiently large voltage across the -250F magnetite, it phase switches back to an electrical conductor. The research team at Rice University believe this may have potential in future phase-switch data storage devices.
Lead researcher, Doug Natelson, associate professor of physics and astronomy, said, "It's fascinating that we can still find surprises in a material like magnetite that's been studied for thousands of years. This kind of finding is really a testament to what's possible now that we can fabricate electronic devices to study materials at the nanoscale." The team does not understand why the magnetite changes electrical properties at around -250F. And now with this new finding that if you apply a sufficient voltage it switches again, and once the voltage is removed, it switches back, adds more questions to be answered.
Magnetite is an iron oxide mineral. It's comprised of four oxygen atoms and three iron atoms and, in crystalline form, comes in distinctive geometric shape. Natelson's experiments involved using two types of magnetite. The first one is called nanorust, which is comprised of tiny particles of magnetite. The second is a single-crystal thin-film form of magnetite. The nanorust was developed at Rice's Center for Biological and Environmental Nanotechnology by Vicki Colvin. The single-crystal variety was developed by Igor Shvets from the University of Dublin's Trinity College.
The team will now set their sights on attempting to isolate the fundamental physics behind the switch. There is also a considerable amount of interest in the next-generation of computers and hard-drives. Such a phase-shifting material could provide usable research data for future products, possibly even becoming a product itself. "So, how much lodestone you got? 8 kilos. And you? Only 4, dude you rock!"
This research was funded by the U.S. Department of Energy.