Princeton University researchers were surprised to see that frustrated magnets exhibit a behavior called the Hall Effect.
Frustrated magnets are materials that are supposed to be magnetic at low temperatures but aren't. When a magnetic field is applied to an electric current flowing through a semiconductor, such as a copper ribbon, the current deflects to one side of the ribbon. This is known as the Hall Effect and is used in sensors for all sorts of devices, from TV remote controls to vehicles' anti-lock braking systems.
According to classical physics, the Hall Effect can only happen in charged particles. Frustrated magnets, which are not charged, were believed to be unable to demonstrate the Hall Effect.
"To talk about the Hall Effect for neutral particles is an oxymoron, a crazy idea," said N. Phuan Ong, a physics professor at Princeton.
However, some physicists postulate that, in very low-temperature conditions, where objects operate according to the laws of quantum mechanics instead of the classical laws of physics, frustrated magnets could possibly exhibit the Hall Effect.
To test this hypothesis, Ong and his colleague chemistry professor Robert Cava and graduate students Max Hirschberger and Jason Krizan used a class of magnets called pyrochlores, which have magnetic moments that should neatly line up under cold temperatures so that all their "spins," a quantum property, should point to a single direction. However, the experiment shows the spins pointed in all sorts of directions.
"All of us were very surprised because we work and play in the classical non-quantum world," said Ong. "Quantum behavior can seem very strange, and this is one example where something that shouldn't happen is really there. It really exists."
The researchers believe the results of their experiment could potentially lead to insight about high-temperature superconductivity, the frictionless transmission of electricity, and could eventually help other scientists develop breakthrough technologies in computing and electronics.
Specifically, the researchers think the study could pave the way for more research on the superconductivity of copper-containing materials known as high-temperature superconductors. Also called cuprates, these materials work even above the low temperatures needed to keep the superconductors in today's machines, such as MRI imaging machines, working.
"Every technological advance has a basis in fundamental science through our curiosity about how the world works," said Cava.
