Stress me, test me, vex me ... boffins seek Hall Effect in frustrated magnets

Physics prof: 'An oxymoron, a crazy idea. AND YET'

Assembled experiment lowered into a high-field magnet system. Image credit: Jason Krizan
Assembled experiment lowered into a high-field magnet system. Image credit: Jason Krizan

Scientists believe a new finding could help future advanced electronics research – and it's all courtesy of some frustrated magnets.

The results of a new experiment could help reveal more details about the way the frictionless transmission of electricity works, it has been claimed.

Boffins at Princeton University in the US tested so-called frustrated magnets, which carry that moniker because their magnetic capability fails to work as it should at low temperatures.

The researchers wanted to see if the vexed magnets would exhibit a behaviour known as the Hall Effect. As they explained:

When a magnetic field is applied to an electric current flowing in a conductor such as a copper ribbon, the current deflects to one side of the ribbon.

This deflection, first observed in 1879 by EH Hall, is used today in sensors for devices such as computer printers and automobile anti-lock braking systems.

But, as noted by Princeton's physics prof N Phuan Ong, such a response should be impossible to expect from neutral particles like frustrated magnets.

"To talk about the Hall Effect for neutral particles is an oxymoron, a crazy idea," Ong added.

The researchers said they wanted to see if frustrated magnets might exhibit the Hall Effect under very cold conditions to allow particles to react to the laws of quantum mechanics, rather than the classical physical laws.

They used a class of magnets called pyrochlores during their study. The team said:

They contain magnetic moments that, at very low temperatures near absolute zero, should line up in an orderly manner so that all of their "spins," a quantum-mechanical property, point in the same direction. Instead, experiments have found that the spins point in random directions. These frustrated materials are also referred to as "quantum spin ice."

Ong added: "These materials are very interesting because theorists think the tendency for spins to align is still there, but, due to a concept called geometric frustration, the spins are entangled but not ordered."

A better understanding of such quantum behaviour could lead to different approaches in computing and electronic devices, the scientists argued in their Large thermal Hall conductivity of neutral spin excitations in a frustrated quantum magnet paper, published in Science this week.

Boffins believe that entanglement is a key ingredient of quantum systems and it's hoped that it can one day be harnessed to build a more powerful quantum computer. ®

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