Evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu${}_{1-x}$Gd${}_x$O

Raman scattering studies as functions of temperature, magnetic field, and Gd-substitution are used to investigate the evolution of magnetic polarons and spin-carrier interactions through the metal-insulator transition in Eu${}_{1-x}$Gd${}_x$O. These studies reveal a greater richness of phase behavior than have been previously observed using transport measurements: a spin-fluctuation-dominated paramagnetic (PM) phase regime for T $>$ T${}^{\ast }$ $>$ T${}_C$, a two-phase regime for T $<$ T${}^{\ast }$ in which magnetic polarons develop and coexist with a remnant of the PM phase, and an inhomogeneous ferromagnetic phase regime for T $<$ T${}_C$.