Carrier density variation in films of Nd0.5Sr0.5MnO3

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 T-C = 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 p(xy)(B) slope due to the anomalous Hall effect is observed. The spontaneous Hall resistivity rho(xy)(star), reflecting the strength of the asymmetric scattering between carriers and localized magnetic moments, is linked to the zero-field resistivity p(xx) via p(xy)(star) proportional to rho(xx)(1.74).