Insulator?Metal Transition in Single and Multiple Phase Manganite La0.67Ca0.33MnO3

N.E. MASSA; H. SALVA; J. A. ALONSO; M. J. MARTÍNEZ-LOPE; M. T. CASAIS.

PHYSICA STATUS SOLIDI B-BASIC RESEARCH

WILEY-V C H VERLAG GMBH

Lugar: Weinheim; Año: 2000 vol. 220 p. 369 - 371

0370-1972

We report on the preparation dependence of the La0.67C0.33MnO3 insulator?metal phase transition. We have found that while resistivity measurements show that sol?gel techniques yield samples with a sharp transition with the lowest Tc at ≈180 K in a highly resistive medium, those prepared under 20 kbar and 1000 °C have an increment of about 80 degrees in their insulator?metal transition at ≈254 K. Intermediate to these results we found that the 1300 °C temperature cycling of sol?gel samples results in two phase compounds with their resistivities peaking at ≈180 K and ≈254 K. Although this also suggests that in these last ones there is a miscibility gap of two distinct ferromagnetic phases, susceptibility measurements only show ferromagnetic saturation at lower temperatures. The 77 K far infrared reflectivity of these compounds is typical ofconducting oxides, their Drude component scaling with the overall resistivities.