EPR Spectrum Formation Mechanism of the Iron-Doped ZnSe

Zinc selenide (ZnSe) doped with iron (ZnSe:Fe) has been obtained by the Bridgman method under excessive pressure of Ar. The microstructure analysis showed the sample has a homogeneous structure, which corresponds to the ZnSe:Fe solid solution. The ZnSe:Fe sample has been examined by X-band electron paramagnetic resonance (EPR) spectroscopy in the temperature range from 5 K to 300 K. The EPR spectrum consists of an unequally broadened EPR line with g = 2.088, a well-resolved line with the g-factor of 4.27, which occurs with decreasing temperature and some low-intensity lines arising at 5 K. Moreover, there are two sets of manganese-related lines due to the hyperfine coupling with
⁵⁵
Mn nuclei, which appear as a concomitant impurity in the studied sample. The mechanism forming of the EPR spectrum was analyzed using Modified Crystal Field Theory (MCFT). It was revealed that the EPR signal at g ~ 2 is caused by the Fe
³⁺
ions, which occupy both octahedral and tetrahedral positions and undergo an off-centering effect. The EPR line with g = 4.27 as well as the low-intensity signals that evident at 5 K are caused by the transitions in the distorted tetrahedral complexes with anionic vacancies.