Oxygen-isotope exchange and cation disorder effects on magneto-transport properties of (Sm1-yGdy)0.55Sr0.45MnO3

Abstract

Detailed systematic studies of the effects of both the cation disorder and the oxygen isotope exchange ¹⁶O → ¹⁸O on the magneto-transport properties of (Sm_1-yGd_y)_0.55Sr_0.45MnO₃ manganites were performed for y between 0 and 1. We investigated changes in the temperature and magnetic field dependence of the magnetization, resistivity and magneto-resistivity, including the effects of the oxygen isotope substitution on the magneto-transport properties of samples with high magneto-resistance and the oxygen-isotope exchange induced metal–insulator transition. Very large cation disorder leads to a formation of the insulating spin-glass state in which no colossal magneto-resistance or field-induced ferromagnetism occurs. There is also no significant effect of the oxygen isotope exchange on samples in the spin-glass state.