A new type of fractal has been discovered in magnetic ice: ScienceAlert

A new type of fractal has been discovered in magnetic ice: ScienceAlert

A new type of fractal has been discovered in magnetic ice: ScienceAlert

Fractal patterns can be found everywhere from snowflakes to lightning to the jagged edges of coastlines. Beautiful to look at, their repetitive nature can also inspire mathematical insights into the chaos of the physical landscape.

A new example of these mathematical quirks has been discovered in a type of magnetic substance known as spin ice, and it could help us better understand how a quirky behavior called a magnetic monopole emerges from its troubled structure.

Spin ices are magnetic crystals that follow similar structural rules to water ice, with unique interactions governed by the spins of their electrons rather than the pushing and pulling of charges. As a result of this activity, they do not have any low energy states of minimal activity. Instead, they almost buzz with sound, even at insanely low temperatures.

Out of this quantum buzz emerges a strange phenomenon – features that act like magnets with only one pole. Although they are not entirely hypothetical magnetic monopole particles some physicists think they can exist in nature, they behave in a similar way that makes them worth studying.

So an international team of researchers recently turned their attention to a spider ice called dysprosium titanate. When small amounts of heat are applied to the material, the typical magnetic rules break and monopoles appear, with the north and south poles separating and acting independently of each other.

Several years ago a team of researchers identified distinctive monopole magnetic activity in the quantum hum of a dysprosium titanate spin ice, but the results left a few questions about the exact nature of these monopole motions.

In this follow-up study, physicists realized that the monopoles were not moving along complete freedom in three dimensions. Instead, they were confined to a plane of 2.53 dimensions within a fixed grid.

The scientists created complex atomic-scale models to show that the monopole motion was confined to a fractal pattern that was erased and rewritten depending on conditions and previous motions.

“When we entered this into our models, fractals came up right away,” says physicist Jonathan HallĂ©n from the University of Cambridge.

“The configurations of the spins created a network that the monopoles had to move. The network branches out like a fractal with just the right dimension.”

This dynamic behavior explains why conventional experiments had previously missed the fractals. It was the noise created around the monopoles that ultimately revealed what they were actually doing and the fractal pattern they followed.

‘We knew something very strange was going on’ says physicist Claudio Castelnovo from the University of Cambridge in the United Kingdom. “The results of 30 years of experiments were wrong.”

“After several failed attempts to explain the noise results, we finally had a eureka moment, when we realized that the monopoles must live in a fractal world and could not move freely in three dimensions, as had always been assumed.”

Breakthroughs like this could lead to incremental changes in the capabilities of science and how materials like spin ice could be used: perhaps in spintronicsan emerging field of study that could provide a next-generation upgrade to the electronics we use today.

“In addition to explaining several puzzling experimental results that have long challenged us, the discovery of a mechanism for the emergence of a new type of fractal has led to a completely unexpected pathway for unconventional motion in three dimensions,” says theoretical physicist Roderich Moessner from the Max Planck Institute for the Physics of Complex Systems in Germany.

The research has been published in Science.



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