Origin of an enhanced colossal magnetoresistance effect in epitaxial Nd0.52Sr0.48MnO3 thin films

Nd0.52Sr0.48MnO3 films of various thicknesses have been prepared by dc magnetron sputtering on single crystal LaAlO3 (001) substrates. Reducing the film thickness leads to a significant suppression of ferromagnetic (FM) ordering and the Curie point falls below the antiferromagnetic (AFM) transition temperature. When this occurs, a huge rise of the magnetoresistance ratio from 400 to 60 000% is observed in an applied magnetic field of 5 T. We surmise that this new kind of the enhanced colossal magnetoresistance effect originates in the FM/AFM competition and the collapse of the charge-ordered state at high magnetic fields, rather than in the regular double-exchange mechanism.