Structural, magnetic and magnetotransport properties of La0.7Pb0.3(Mn1-xNix)O-3 (0.1 <= x <= 0.3) CMR manganites.

Structural and magnetic properties of La0.7Pb0.3(Mn1-xNix)O-3 (0.1 <= x <= 0.3) manganites are reported, Samples were fabricated by the sol-gel low-temperature method. At room temperature, the first structural characterization of all phases indicated the rhombohedral space group (R (3) over barc). All compositions show ferromagnetic behaviour and magnetoresistance. The measured low-temperature magnetic moment and the Curie temperature continuously decrease, with respect to the undoped composition, as Mn ions are substituted progressively by Ni. This is interpreted in terms of direct substitution of Mn3+ by low-spin (LS.) Ni3+ ions. The measured magnetoresistance reaches 46 % for the 10 % Ni-doped composition and 28 % for the 30 % Ni-doped one at the corresponding Curie temperature. The resistivity behaviour of all the studied compounds is fully determined by the intergrain conduction mechanism, with grain sizes in the range 20-45 nm. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).