International Journal of Modern Physics B, Condensed Matter Physics, Statistical Physics, Applied Physics vol:14 issue:29-31 pages:3735-3740
We performed a comparative study on the colossal negative magnetoresistivity and the Hall effect in thin films of the manganese perovskite La1-xCaxMnO3 with x = 0.3 and x = 0.67. The underdoped sample (x = 0.3) undergoes a phase transition from a paramagnetic semiconductor to a ferromagnetic quasimetal at the Curie temperature T-C = 280 K,while the overdoped compound (x = 0.67) stays a paramagnetic semiconductor at all temperatures. Both materials show colossal negative magnetoresistivity, albeit on considerably different temperature- and field scales, depending on the magnetic interactions between neighbouring Mn ions. According to the Hall data, the charge carriers in the underdoped material are hole-type, partially compensated by an electron-type contribution. The overdoped system shows electronic carriers with a thermally activated concentration. The ordinary Hall effect is in both compounds superimposed by an anomalous Hall contribution with a sign opposite to the intrinsic charge-carrier type.