Magnetic and magnetotransport properties of the (La0.67Pb0.33)(Mn1−xFex)O3 (0 ≤ x ≤ 0.1) compounds

A study of magnetic and electrical transport properties of Fe-doped colossal magnetoresistive manganese perovskites (La0.67Pb0.33)(Mn1−xFex)O3 (x = 0, 0.01, 0.03, 0.06 and 0.1) is presented. Polycrystalline compounds were prepared by the sol–gel low-temperature method. The dc magnetization measured in the fields 50 Oe and 1 kOe and hysteresis loops up to 89 kOe were measured from 4 K up to 400 K. Four-probe magnetoresistance measurements have been performed in the same temperature range at the applied magnetic fields up to 80 kOe. It was found that the substitution of Fe for Mn results in a reduction of the saturation magnetic moment, an increase of the resistivity, as well as a decrease of the Curie (TC) and metal–insulator (TM–I) transition temperatures. The x = 0.1 compound exhibits the largest magnetoresistance effect of about 300% around its TM–I temperature in the applied field of 80 kOe. The resistivity above TC for the compounds follows the thermally activated behaviour with the activation energy of about 0.12 eV. The results confirm that Fe substitutes for Mn3+, forming Mn4+/Fe3+ pairs which do not support the double exchange interaction. This strongly affects the magnetic and magnetotransport properties as compared with those of the Fe undoped compound.