SUBMILLIMETER BACKWARD-WAVE OSCILLATOR SPECTROSCOPY OF THE RARE-EARTHORTHOFERRITES

A complex dielectric permittivity and a complex magnetic permeability of the orthoferrites RFeO(3) (R = Y, Tm, Dy, Gd, Ho, Er, Tb) and Y1-xL uxFeO3 have been investigated at submillimeter wavelengths v = 100-100 0 GHz. The parameters of the two antiferromagnetic resonance modes (re sonance frequencies, linewidths and mode contributions to the static p ermeability) have been obtained. We observed the electronic transition s inside the Tm3+, Er3+, Ho3+ ground multiplets and found a strong inf luence of this excitations on the AFMR mode behavior. A permittivity i ncrease (up to 30%) in TmFeO3 resulted from the electrodipolar transit ions in Tm3+ was revealed.