Effect of Ga doping on magnetotransport properties in collosal   magnetoresistive La0.7Ca0.3Mn1-xGaxO3 (0 < x < 0.1)
  Samples of La0.7Ca0.3Mn1-xGaxO3 with x = 0, 0.025, 0.05 and 0.10 were prepared by standard solid-state reaction. They were first characterized chemically, including the microstructure. The magnetic properties and various transport properties, i.e. the electrical resistivity, magnetoresistivity (for a field below 8T), thermoelectric power and thermal conductivity measured each time on the same sample, are reported. The markedly different behavior of the x = 0.1 sample from those with a smaller Ga content, is discussed. The dilution of the Mn3+/Mn4+ interactions with Ga doping considerably reduces the ferromagnetic double exchange interaction within the manganese lattice leading to a decrease of the Curie temperature. The polaron binding energy varies from 224 to 243 meV with increased Ga doping. 
Marek Pekala (Univ. Warszawa), Jan Mucha (PAS, Wroclaw), Benedicte   Vertruyen, Rudi Cloots, and Marcel Ausloos (S.U.P.R.A.T...