SIMULTANEOUS STRUCTURAL, MAGNETIC, AND ELECTRONIC-TRANSITIONS IN LA1-XCAXMNO3 WITH X=0.25 AND 0.50

The magnetic transitions in La1-xCaxMnO3 (x = 0.25,0.50) were studied by synchrotron x-ray and neutron powder diffraction. For x = 0.25 the large Delta V = 0.13% at T-C is due to the simultaneous insulator-to-metal transition. For x = 0.50 below T-C we observed a drastic decrease of the b axis and an increase of the a and c axes, due to a Jahn-Teller distortion of MnO6 octahedra. The ferromagnetic transition for x = 0.50 is accompanied by an unusual peak broadening terminating at T-N. This newly observed behavior can be explained assuming that multiple intermediate phases are simultaneously present in the sample.