Pressure effects in ferromagnetic manganites and carrier scattering by disordered magnetic rare earths

The influence of hydrostatic pressure on the transport properties of (La1-x Rx)(0.67)Ca0.33MnO3 (R = Y,Tb) ferromagnetic manganites is investigated. Th e enhancement of the Curie temperature T-C under pressure agrees with previ ous data. In the paramagnetic range, the resistivity can be represented by a Mott localisation law, with a characteristic temperature T-0 decreasing w ith pressure. The variation of T-C with pressure is compared to the effect induced by replacing La by a magnetic rare earth in (La1-xRx)(0.67)Sr0.33Mn O3 manganites (R = Pr, ..., Tm). The main effect is not related to the decr ease of the mean radius of the cation, but to an additional scattering by t he magnetic moment of the rare earth.