MIT researchers have demonstrated experimentally the existence of a fundamentally new kind of magnetic behavior, adding to the two previously known states of magnetism.
Ferromagnetism — the simple magnetism of a bar magnet or compass needle — has been known for centuries. In a second type of magnetism, antiferromagnetism, the magnetic fields of the ions within a metal or alloy cancel each other out. In both cases, the materials become magnetic only when cooled below a certain critical temperature.
The Quantum Spin Liquid (QSL) is a solid crystal, but its magnetic state is described as liquid: Unlike the other two kinds of magnetism, the magnetic orientations of the individual particles within it fluctuate constantly, resembling the constant motion of molecules within a true liquid.
MIT physicists grew this pure crystal of herbertsmithite in their laboratory. This sample, which took 10 months to grow, is 7 mm long (just over a quarter-inch) and weighs 0.2 grams. Image: Tianheng Han
There is no static order to the magnetic orientations, known as magnetic moments, within the material, Lee explains. “But there is a strong interaction between them, and due to quantum effects, they don’t lock in place,” he says.
The material itself is a crystal of a mineral called herbertsmithite. Lee and his colleagues first succeeded in making a large, pure crystal of this material last year — a process that took 10 months — and have since been studying its properties in detail.
It may take a long time to translate this “very fundamental research” into practical applications, Lee says. The work could possibly lead to advances in data storage or communications, he says — perhaps using an exotic quantum phenomenon called long-range entanglement, in which two widely separated particles can instantaneously influence each other’s states. The findings could also bear on research into high-temperature superconductors, and could ultimately lead to new developments in that field, he says.
SOURCE – MIT News