Comparative Hall studies in the electron- and hole-doped manganites La0.33Ca0.67MnO3 and La0.70Ca0.30MnO3

A comparative study of the Hall effect and the longitudinal resistivity of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$ $(x=0.30$ and $x=0.67)$ thin films has been performed. The underdoped samples $(x=0.30)$ show a semiconductor-to-quasimetal transition, and a colossal magnetoresistance (CMR) effect around ${T}_{C}=280\mathrm{K}.$ The samples with $x=0.67$ stay semiconducting at low temperatures, and show a CMR effect up to $99%$ in magnetic fields of 50 T. In both compounds an extraordinary Hall contribution was found, with opposite sign to the regular Hall effect. For $x=0.30$ the charge carriers are hole-type, whereas for $x=0.67$ we observe electron-type carriers. The extraordinary Hall coefficient ${R}_{A}$ can be linked to the longitudinal resistivity ${\ensuremath{\rho}}_{\mathrm{xx}}$ via ${R}_{A}\ensuremath{\propto}{\ensuremath{\rho}}_{\mathrm{xx}}^{\ensuremath{\alpha}}$ with $\ensuremath{\alpha}=1.38$ for $x=0.30,$ and $\ensuremath{\alpha}=0.60$ for $x=0.67.$