Breaking reciprocity in optical systems is enabling the possibility of implementing devices with unidirectional wave propagation. Currently, there is an active search for suitable material with an efficient nonreciprocal response at the terahertz (THz) frequency range. Ideally, such material should allow low-loss operation without an external magnetic field at room temperature. Gyrotropic hexaferrite ceramic is highly promising for achieving optical isolation in the THz spectral range. Here, we demonstrate a broadband self-biased THz isolator based on magnetized aluminum-substituted barium hexaferrite. We reveal the necessary surface density of the hexaferrite sample for the realization of THz isolation. The proposed device exhibits no less than 30 dB of isolation from 0.2 to 1 THz. Moreover, we show that the gyrotropy properties of hexaferrite ceramics can be reasonably predicted by their magnetic properties. This device is expected to be useful for applications where one-way propagation of broadband THz wave is desired.

The results of calculation of the charge-carrier concentration in bismuth–antimony films on substrates with different coefficients of thermal expansion are reported. The antimony content in...

The results of studying the resistivity, magnetoresistance, and Hall coefficient of thin films of bismuth and the bismuth–antimony system on a borosilicate-glass substrate under plane tensile strain are presented. Deformation is created by a specially developed method that allows a change in its magnitude directly during measurement of the film properties. The films are obtained by thermal evaporation in vacuum. Varying the technological modes made it possible to obtain films of various structures: from small blocks to single crystal. Based on the experimental results, within the framework of the two-band approximation, the concentrations of charge carriers and the positions of the energy extrema of the valence and conduction bands relative to the chemical potential level are calculated. It is shown that the two-band approximation is insufficient for describing the properties of films of the studied compositions under plane tensile strain.

In our paper we propose the method for measuring the thermoelectric power of thin semimetals films and narrow-gap semiconductors on the thin substrates. This method eliminates the occurrence of mechanical stresses due to different thermal expansion coefficients of the substrate material and the gradient plates. We compared the thermopowers' temperature dependences obtained by the new method of measuring and by the standard method for thin films Bi_1–x Sb _x on a substrate of mica. With the help of our method it is possible to get more reliable results for thin films of semimetals and narrow-gap semiconductors formed on thin substrates.