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May 24, 2012

Engineered materials: Custom-made metamaterial magnets

A novel approach to designing artificial materials could enable magnetic devices with a wider range of properties than those now available.

Luk'yanchuk and the team mathematically modelled a two-dimensional array of metamolecules comprising a silicon sphere next to a partially incomplete copper ring. They studied the influence of both the sphere and the split ring on the magnetic component of an incident electromagnetic wave — a property known as magnetization.

"When the two structures were more than one micrometer apart, they both acted to increase the local magnetic field," says Luk’yanchuk. However, they started to interact when moved closer together, and the researchers observed that the magnetization of the split ring decreases and even becomes negative for separations smaller than 0.5 micrometers.

This situation is somewhat analogous to the magnetic ordering in ‘natural’ materials. When all the atoms contribute in a positive way to a material’s magnetic properties, the material becomes a ferromagnet. However, when alternating regions of the material have opposite magnetization, the material is said to be antiferromagnetic.

"We demonstrate that our hybrid lattices of metamolecule exhibit distance-dependent magnetic interaction, opening new ways for manipulating artificial antiferromagnetism with low-loss materials," explains Luk'yanchuk.


An array of metamolecules comprising silicon spheres and copper split-rings can be used to control magnetization waves. © 2012 American Chemical Society



Although the analogy between metamaterials and magnetic materials is not a perfect one, most metamaterials are said to be ferromagnet-like. The design proposed by Luk'yanchuk and the team closely mimics antiferromagnetic ordering, and this opens an opportunity for researchers to study antiferromagnetic phenomena in metamaterials. One notable example is giant magnetoresistance, a phenomenon that is at the heart of modern electronic memories.

Luk'yanchuk affirms that a metamaterial analog would offer exciting research prospects. "We believe that our work has the potential to make a strong impact towards the development of on-chip integrated solutions for reconfigurable and optically-controlled metamaterials."


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