  We suggest a principle for isolation of circularly polarized waves in
magnetically active extreme-parameter metamaterials. Using theoretical analysis
and numerical simulations, we show that metamaterials with extreme parameters,
such as epsilon-near-zero materials (ENZ), when merged with magneto-optical
materials, become transparent for forward circularly polarized waves of a given
handedness and opaque for backward propagating waves of the same handedness. We
theoretically study two possible implementations of such hybrid materials: (1)
the case of metal-dielectric stacks; and (2) rectangular waveguide near its
cut-off frequency. We prove that these structures can be utilized as compact
isolators for circularly polarized waves.
