Negative permeability from split ring resonator arrays

Summary form only. The range of values observed for the magnetic permeability, /spl mu/(/spl omega/), appears to be more restricted than the values observed for the electric permittivity, /spl epsi/(/spl omega/), where very large, and even negative values are observed. This is in part due to the simple fact that there are no magnetic monopoles to provide the analogous response to that of electrons. In particular, as one moves away from zero frequency, the magnitude of the magnetic response from most materials, or /spl mu/(/spl omega/), decreases rapidly, and has never been observed to take negative values. While the general lack of magnetic response is observed to be the case, Maxwell´s equations do not preclude a material having a large /spl mu/(/spl omega/), either positive or negative. The essential requirement on the material constants appears only to be d/d and d/d for frequency-dependent materials. Pendry et al. (1999) have introduced conducting nonmagnetic split ring resonators (SRRs), and predicted that periodic arrays of SRRs can have a resonantly enhanced effective permeability displaying frequency regions with large positive or negative values. Combining numerous SRRs into a lattice forms an effective medium, for which there exists a band of frequencies where the effective permeability is negative. The SRR medium offers the possibility of engineering materials to respond to time-varying magnetic fields as well as time-varying electric fields. Combining such composite media with standard materials offers the potential to yield novel and advantageous electromagnetic devices.