1. Department of PhysicsMartin Luther University Hallevon‐Danckelmann‐Platz 306120 HalleGermany
2. Ioffe Physico‐Technical Institute194021 St. PetersburgRussia
3. Institute of Ion‐Plasma and Laser Technologies (Institute of Electronics)700170 TashkentUzbekistan
4. Faculty of Science, Department of PhysicsMinia University61519 MiniaEgypt
5. Leibniz Institute for Crystal GrowthD‐12489 BerlinGermany
6. St. Petersburg State Polytechnical University195251 St. PetersburgRussia