  We report occurrence of large magnetoresistance in lightly doped
antiferromagnetic paraelectric EuTiO3. Reports of magnetoresistance in
rare-earth titanates (RTiO3 oxides) are very scarce because they are highly
insulating at low temperatures. EuTiO3 is an insulator at 2.5 K and 1% La3+
substitution for Eu2+ lowers the resistivity over five orders of magnitude at
2.5 K. It is shown that Eu0.99La0.01TiO3 which is antiferromagnetic below T=
5.43 K shows large magnetoresistance over a wide temperature. At 2.5 K,
magnetoresistance is -42 % for H = 6 kOe and it increases to -75 % for H = 7 T.
Even at 50 K which is ten times higher than Neel temperature, magnetoresistance
is very significant (-20 % for H = 7 T). It is suggested that 4f spins on Eu2+
ion is strongly exchange coupled to doped electron in Ti-3d band via f-d
interation and field-induced suppression of 4f spin fluctuations decrease
spin-disorder scattering experienced by 3d electrons. In view of our results,
it will be interesting to investigate magnetoresistance of other rare earth
titanates.
