  We describe the design of two types of metamaterials aimed at enhancing
terahertz field pulses that can be used to control the magnetic state in
condensed matter systems. The first structure is a so-called "dragonfly"
antenna, able to realize a five-fold enhancement of the impinging terahertz
magnetic field, while preserving its broadband features. For currently
available state-of-the-art table top sources, this leads to peak magnetic
fields exceeding 1 T. The second structure is an octopole antenna aimed at
enhancing a circularly-polarized terahertz electric field, while preserving its
polarization state. We obtain a five-fold enhancement of the electric field,
hence expected to exceed the 1 MV/cm peak amplitude. Both our structures can be
readily fabricated on top of virtually any material.
