Evolution of Magnetic Polarons and Spin-Carrier Interactions through the Metal-Insulator Transition in [Formula presented]

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 [Formula presented]. These studies reveal a spin-fluctuation-dominated paramagnetic (PM) regime for [Formula presented], and a coexistence regime for [Formula presented] 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.