Structural and magnetic phase diagram an room temperature CMR effect of La1-xAgxMnO3

The study of the structural and magnetic phase diagram of the manganites La1-xAgxMnO3 shows similarity with the La1-x'Srx'MnO3 series, involving a metallic ferromagnetic domain at relatively high temperature (approximate to 300 K). The Ag-system differs from the Sr-one by a much smaller homogeneity range (x less than or equal to 1/6) and the absence of charge ordering. But the most important feature of the Ag-manganites deals with the exceptionally high magnetoresistance (-25%) at room temperature under 1.2 T, that. appears, for the composition x = 1/6. The latter is interpreted as the coincidence of the optimal double exchange condition (Mn3+:Mn4+ = 2) with T-max = 300 K (maximum of the rho(T) curve in zero field). (C) 2003 Elsevier Science Ltd. All rights reserved.