Structural and physical properties of double-layered manganites La2-2xCa1+2xMn2O7 with 0.5 <= x <= 1.0 - art. no. 020405

Structural and physical properties of the double-layered manganites La2-2xC a1+2x\Mn2O7 (0.5 less than or equal tox less than or equal to1.0), prepared under a high pressure of 4.5 GPa, have been systematically investigated. A charge-ordered state has been revealed at low temperatures in the samples with 0.6 less than or equal tox less than or equal to0.75. The x = 0.6 mate rial undergoes the charge-ordering transition at similar to 280 K and, succ essively, a ferromagnetic (FM) transition at similar to 160 K with evident colossal magnetoresistance effects under applied magnetic fields. A phase s eparation resulting from the competition between the charge-ordered state a nd the FM state is observed in the x = 0.6 material below 160 K.