Magnetic polaritons in XF2 (X=Mn, Fe) canted antiferromagnets

We discuss the magnetic polariton modes which propagate in a two-sublattice , uniaxial Heisenberg antiferromagnet, for the case where an external magne tic field is applied perpendicular to the easy axis of the material. At hig h magnetic fields, a large magnetization component normal to the easy axis will be induced, and we may expect to find a magnetic field induced surface polariton mode, which propagates parallel to the easy axis, with nonrecipr ocal propagation characteristics. We confine our discussion to antiferromag nets, which have a body-centered tetragonal structure (e.g., XF2, with X = Mn and Fe). The spectra show that the nonreciprocal propagation of the surf ace polariton is much more evident in MnF2 crystals. (C) 2001 American Inst itute of Physics.