OXYGEN-ISOTOPE EFFECT ON THE FIELD-INDUCED METAL-INSULATOR-TRANSITIONIN PR2 3CA1/3MNO3/

Resistivity and magnetostriction measurements have been performed on t he oxygen-isotope substituted (O-16 and O-18) samples of Pr2/3Ca1/3MnO 3 under magnetic fields up to 12 Tesla. Without applying magnetic fiel d, both isotope samples have qualitatively similar transport and latti ce properties, showing a crossover from a charge localised (CL) to a c harge ordered (CO) state at the same temperature. In both isotope samp les, there is an insulator to metal (I-M) transition induced by a magn etic held, but the magnetic field that induces the I-M transition is m uch higher for the O-18 sample than for the O-16 sample. Our results s how that a heavier oxygen isotope mass favours the insulating state an d that the CO transition has no significant correlation with the latti ce dynamics. (C) 1998 Elsevier Science Ltd.