New research into the Third Law of Thermodynamics and the odd behaviors of spin ice could have implications for data storage and more, with nanotech scientists finding unexpected behaviors at near-absolute zero. The study, carried out at University College London, created thin films of spin ice – which shows magnetic properties, and normally would be assumed to be the only thing not to fully freeze at absolute zero – for the first time, and then demonstrated how those films could be manipulated.
The Third Law of Thermodynamics states that “the entropy of a perfect crystal, at absolute zero kelvin, is exactly equal to zero.” However, spin ice was believed to be the one exception to the rule, its inherent atomic magnetic moments keeping up their random “spins” even as -273 degrees centigrade is approached.
However, by growing a film of spin ice just a few nanometers thick and then submitting it to X-ray diffraction, the UCL researchers discovered that wasn’t actually the case. In fact, at a half-degree above absolute zero, the entropy within the spin ice disappeared, indicating that the Third Law does indeed hold true.
“Using X-ray diffraction at the LCN, the researchers showed that the films are slightly strained by the ‘substrate’ on which they are grown, which causes the loss of entropy” UCL
By manipulating the substrate strain, the researchers believe they will be able to control the spin ice state, and in the process unlock “new possibilities for the control and manipulation of magnetricity and magnetic monopoles” UCL’s Dr. Laura Bovo says.
Magnetricity, first demonstrated experimentally in 2009 at UCL, is the magnetic equivalent of electricity. Whereas normally magnetic charge splits into north and south poles, even down to the molecular level, in spin ice it’s possible to create magnetic monopoles, or individual magnetic poles that can move around independently.
Implementing this research into something practical is still some ways off, but there are suggestions that the tiny, individually charged monopoles – if manipulated correctly – could be used for incredibly dense storage, exponentially more capacious than today’s hard-drives.