A high-sensitivity far infrared magneto-optical spectrophotometer, cap
able of measuring the dependences of the transmission and reflection o
f samples over a wavelength range of 40 to 1200 mum on the temperature
and the magnetic field, is described. The modular design enables meas
urements in both partly or fully polarized light, as well as obtaining
dependences on the orientation of the light polarization plane with r
espect to the sample axes. Examples of the temperature and magnetic fi
eld dependent transmission spectra of a YbIG sample are demonstrated.