H Rho, CS Snow, SL Cooper, Z Fisk, A Comment, J-P Ansermet
Phys Rev Lett
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 spin-fluctuation-dominated paramagnetic (PM) regime for T>T*>T(C), and a coexistence regime for T<T* in which spin polarons develop and coexist with remnants of the PM phase. They further show a strong connection between spin cluster formation and the dramatic field effects observed in these materials.