Magneto-optical effects of the antiferromagnetic semiconductor EuTe

The Faraday rotation and the absorption of EuTe have been measured on thin films in the fundamental absorption region from 2·0 to 4·3 eV. Above the Néel temperature,T_N=9·6 °K, we observe in the energy range of the 4f⁷–4f⁶ 5dt_2g transition, one minimum and two main maxima of rotation. The temperature dependence of the maxima is found to be different: for one extremum the rotation resembles the magnetization curve of an antiferromagnet with a maximum at the Néel temperature; for the second, however, the rotation shows a ferromagnetic dependence on temperature with a point of inflexion at the Néel temperature and saturation for lower temperatures.This ferromagnetic behaviour within the antiferromagnetic structure of EuTe can be explained by assuming a ferromagnetic superlattice which gives rise to a magnetic Brillouin zone. Thus the ferromagnetic peak is attributed to transitions from the localized 4f ground state to the new zone boundaries.We wish to thank Mr. H. P. Staub for technical assistance, Dr. E. Kaldis for supplying the substances and Dr. J. Muheim for the mass spectroscopic analysis. Financial support by the Schweizerische Nationalfonds zur Förderung der wissenschaftlichen Forschung is gratefully acknowledged.