Carrier density variation in films of Nd 0.5 Sr 0.5 MnO 3

Abstract
The carrier density in thin films of Nd0.5Sr0.5MnO3, as derived from Hall measurements, shows a distinct change at the paramagnetic (PM)-ferromagnetic (FM) transition around TC = 225 K. In the PM-semiconducting regime the density is n = 0.30 holes per unit cell and increases in the FM-semimetallic regime to n = 0.49. The magnetoresistance effect in the semimetallic phase is due to a field-induced increase of the carrier mobility, while the carrier density is unaffected. In the low-field limit an extraordinary enhancement of the ρxy(B) slope due to the anomalous Hall effect is observed. The spontaneous Hall resistivity ρxy, reflecting the strength of the asymmetric scattering between carriers and localized magnetic moments, is linked to the zero-field resistivity ρxx via ρxy ∝ ρxx1.74.