Negative refraction gets natural. ‘Physicists in Germany claim to have found the first naturally occurring material that has a negative, rather than a positive, refractive index. The material – a metallic ferromagnet – is very different from all other negative-refractive-index materials known to date, which have had structures that have been artificially engineered in the laboratory. The ferromagnets, which have been shown to exhibit negative refraction up to gigahertz frequencies, could be used in novel devices such as superlenses (Phys. Rev. Lett. 98 197401).
Devices that have exploited this odd effect to date, such as high-resolution “superlenses”, have all used negative-refraction materials created artificially in the lab, such as arrangements of copper rings or rods. This is because materials with both negative permeability and permittivity have not been found in nature. But now Andrei Pimenov of the Universität Würzburg along with colleagues at other German institutions has shown that negative refraction can crop up in metal ferromagnets – in other words, in natural materials.’