Interplay between transport, magnetic-, and structural properties of Mn-perovskites with various doping level

We performed a comparative study on the colossal negative magnetoresistivit y and the Hall effect in thin films of the manganese perovskite La1-xCaxMnO 3 with x = 0.3 and x = 0.67. The underdoped sample (x = 0.3) undergoes a ph ase transition from a paramagnetic semiconductor to a ferromagnetic quasime tal at the Curie temperature T-C = 280 K,while the overdoped compound (x = 0.67) stays a paramagnetic semiconductor at all temperatures. Both material s show colossal negative magnetoresistivity, albeit on considerably differe nt temperature- and field scales, depending on the magnetic interactions be tween neighbouring Mn ions. According to the Hall data, the charge carriers in the underdoped material are hole-type, partially compensated by an elec tron-type contribution. The overdoped system shows electronic carriers with a thermally activated concentration. The ordinary Hall effect is in both c ompounds superimposed by an anomalous Hall contribution with a sign opposit e to the intrinsic charge-carrier type.