Interband Faraday and Kerr rotation and magnetization of Pb1-xEuxTe in theconcentration range O < x <= 1

Faraday and magneto-optical Kerr effect has been used for the investigation of the band alignment as well as of the magnetic properties of epitaxial l ayers of the ternary alloy system Pb1-xEuxTe (0 less than or equal to x les s than or equal to 1) grown on BaF2 substrates. Due to the wide range of tr ansition energies (0.19 eV less than or equal to E-g less than or equal to 2.25 eV) the experiments had to be performed in the spectral range from mid infrared to visible light. Data were collected at temperatures between 1.8 and 250 K and in magnetic fields up to 7 T. Concomitant magnetization measu rements (B = 1 T) were performed with a superconducting quantum interferenc e device (SQUID) magnetometer and compared with measurements of the x depen dence of the Verdet constant. The variation of the fundamental absorption g ap with Eu content can be understood in terms of the relative energetic pos ition of PbTe-related band edges and Eu 4f and 5d levels: Delta E-g/Delta(x ) = 4.48 eV for x < 0.06; Delta E-g/Delta x = 2.03 eV for 0.06 < x < 0.6. F or x > 0.8, the electronic transitions are identified to be EuTe-like. The most striking feature is a sign reversal of Verdet's constant around x = 0. 15, which is attributed to a crossover of Faraday rotation caused by band e lectrons (holes) and interacting pairs of magnetic ions and a metal-insulat or transition. An antiferromagnetic phase transition is observed for x > 0. 8 in magneto-optics as well as in SQUID magnetometry. [S0163-1829(99)03235- X].