Terahertz and sub-terahertz spectroscopy of magnetic excitations in solids

Various kinds of magnetic excitations (antiferromagnetic resonances, impurity modes, crystal field transitions) are studied in La/sub 1-x/Sr/sub x/MnO/sub 3/ manganites and molecular cluster Mn/sub 12/-ac by means of quasioptical BWO spectroscopic technique. Different measurement regimes (transmittivity and reflectivity vs frequency and/or magnetic field for a definite polarization) enable to extract spectra of magnetic permeabilities /spl mu//sup '/(/spl nu/) and /spl mu//sup "/(/spl nu/) and identify the origin of observed excitations.