Magnetic and electrical properties of Nd-0.66(Sr1-yLiy)(0.34)MnO3 manganites

We present X-ray diffraction, magnetization, electrical resistivity, and magnetoresistance data for Nd-0.66(Sr1-yLiy)(0.34)MnO3 ceramics with y = 0, 0.05, 0.1, 0.2 and 0.3 in the temperature range 50 < T < 400 K and in fields up to 0.5 T. We find that Li substitution is possible up to y less than or equal to0.3 and generally enhances the resistivity and the magnetic randomization. Nevertheless, the resistivity curves still show the characteristic hump-like structure indicative of a combined ferromagnetic-paramagnetic metal-insulator transition, and a significant magnetoresistance is observed. The increase of the resistivity with Li content is ascribed to a blocking of Zener bonds associated with the charge unbalancing effect of Li+. (C) 2001 Elsevier Science B.V. AU rights reserved.