Magnetotransport Properties of $CaTi_xRu_{1-x}O_3$ (x=0, 0.07)

Electrical resistance, transversal magnetoresistance and the Hall effect were studied on polycrystalline $CaTi_xRu_{1-x}O_3$ (x=0, 0.07) samples using a conventional Quantum Design PPMS-9 equipment in the temperature range 2-300 K and magnetic field up to 9 T. Substantial differences were found between the two samples: (i) opposite to the metallic character of $CaRuO_3$, the substituted sample has insulating-like electrical resistance;(ii) the magnetoresistance of the substituted sample changes the sign from negative to positive values with increasing temperature. The magnetoresistance of $CaRuO_3$ is negative, the sign reversal is induced by magnetic field and only at temperatures below 15 K, such a behaviour is predicted for clustered systems;(iii) the Hall voltage in pure $CaRuO_3$ also changes sign from negative to positive values above 35 K. This temperature coincides with the observed magnetic transition temperature, indicating that the magnetic state and the carrier character interrelate