The paper proposes the magnetically controlled polarization-sensitive filter operating in the range of 0.2 to 1.5 THz. This filter is based on the created magnetic fluid comprising 5BDSR (FeNbCuMoCoBSi) amorphous alloy particles 50 μm in size and synthetic motor oil 5W-40. It is shown that the particle control in the magnetic fluid assists in the creation of a diffraction grating equivalent.