Spin Liquid Magnetism

Superconductivity is a state that occurs in some materials, at low temperatures, where there is little or no resistance to movement of electric charge. Electron “spin” is a term used to describe angular momentum (spin) observed in the electric and magnetic charges of electrons. Normally, an object that is magnetic has the magnetic spin of its electrons aligned together. In 1973, Phil Anderson suggested that a spin “liquid” state may exist where electron spin states are not aligned and fluctuate. A few years later, he went on to propose that spin liquid states are associated with high temperature superconductors. High temperature superconductors have great potential to advance electronics.

A new spin on superconductivity?, Mar 29, 2011 – [mit.edu]

MIT scientists have synthesized, for the first time, a crystal they believe to be a two-dimensional quantum spin liquid: a solid material whose atomic spins continue to have motion, even at absolute zero temperature.

The crystal, known as herbertsmithite, is part of a family of crystals called Zn-paratacamites, which were first discovered in 1906. Physicists started paying more attention to quantum spin liquids in 1987, when Nobel laureate Philip W. Anderson theorized that quantum spin liquid theory may relate to the phenomenon of high-temperature superconductivity, which allows materials to conduct electricity with no resistance at temperatures above 20 degrees Kelvin (-253 degrees Celsius).

MIT researchers discover a new kind of magnetism – December 19, 2012 – [mit.edu]

Following up on earlier theoretical predictions, MIT researchers have now 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 prediction and discovery of antiferromagnetism — the basis for the read heads in today’s computer hard disks — won Nobel Prizes in physics for Louis Neel in 1970 and for MIT professor emeritus Clifford Shull in 1994.

“We’re showing that there is a third fundamental state for magnetism,” says MIT professor of physics Young Lee. The experimental work showing the existence of this new state, called a quantum spin liquid (QSL), is reported this week in the journal Nature, with Lee as the senior author and Tianheng Han, who earned his PhD in physics at MIT earlier this year, as lead author.

The 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.

SEE ALSO:
1925 – electron “spin”

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