Virtual Bound States and Configurational Mixing inSm1−xYxSAlloys

Resistivity and Hall effect measurements have been made on ${\mathrm{Sm}}_{1-x}{\mathrm{Y}}_x\mathrm{S}$ alloys which exhibit black to gold phase transitions as a function of temperature and composition, similar to SmS under pressure. The results indicate that in the gold phase there is a virtual bound state at the Fermi level which causes additional scattering and suppresses the Hall effect. In the black phase, the virtual bound state is below the Fermi level and does not contribute to the Hall effect.