Giant negative magnetoresistance of spin polarons in magnetic semiconductors–chromium-doped Ti2O3 thin films

Epitaxial Cr-doped Ti2O3 films show giant negative magnetoresistance up to −365% at 2K. The resistivity of the doped samples follows the behavior expected of spin (magnetic) polarons at low temperature. Namely, ρ=ρ0exp(T0∕T)p, where p=0.5 in zero field. A large applied field quenches the spin polarons and p is reduced to 0.25 expected for lattice polarons. The formation of spin polarons is an indication of strong exchange coupling between the magnetic ions and holes in the system.