Pb 1−x Gd x Te a New Semimagnetic Semiconductor with Rare Earths

Pb 1− x Gd x Te, a new semimagnetic semiconductor, containing gadolinium as a rare earth element is synthesized. Its magnetic susceptibility, transport and optical properties are determined in the temperature range of 4.2 to 300 K using magnetic field intensities up to 6 T. The interaction between the Gd 3+ ions are found to be slightly antiferromagnetic. The measured Hall mobilities of the samples with low gadolinium concentration (1 at% nominal value) are extremely high (4 × 10 6 cm 2 V −1 s −1 ) at 4.2 K. They are comparable with the mobilities reported in superlattices. The large static dielectric constant of the PbTe host lattice is invoked to serve to shield out the electric fields of the ionized impurities and defects, minimizing impurity scattering. In addition, at low gadolinium concentrations, no Schubnikow‐de Haas oscillations are found although all the required conditions for them are satisfied. In this sample the Fermi level is 16.9 meV above the conduction band edge. It is argued consequently, that all the Landau levels passed the Fermi level due to the internal magnetic field induced by the rare earth ions. At higher gadolinium concentrations, 2 and 5 at%, the Fermi level moves up to 338 and 478 meV in the conduction band. Consequently, the internal magnetic field does not pre‐empt the effect of the external magnetic field. This results in the appearance of the Shubnikow‐de Haas oscillations, as expected.