Negative refraction in natural ferromagnetic metals
Institute of Solid State Physics, Vienna University of Technology - A-1040 Vienna, Austria, EU
2 I. Physikalisches Institut, Universität Göttingen - 37073 Göttingen, Germany, EU
Accepted: 17 June 2011
It is generally believed that Veselago's criterion for negative refraction cannot be fulfilled in natural materials. However, considering imaginary parts of the permittivity (ε) and permeability (μ) and for metals at not too high frequencies the general condition for negative refraction becomes extremely simple: Re(μ)<0⇒Re(n)<0 and may be fulfilled for such natural ferromagnetic metals as nickel, iron, or cobalt. Here we demonstrate experimentally that in pure cobalt and Fe/Co alloy the negative values of the refractive index can indeed be achieved close to the frequency of the ferromagnetic resonance. Large values of the negative refraction can be obtained at room temperature and they can easily be tuned in moderate magnetic fields.
PACS: 78.20.Ci – Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity) / 41.20.Jb – Electromagnetic wave propagation; radiowave propagation / 76.50.+g – Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances; spin-wave resonance
© EPLA, 2011