LOW-TEMPERATURE MAGNETORESISTANCE AND THE MAGNETIC PHASE-DIAGRAM OF LA1-XCAXMNO3

The complete phase diagram of a ''colossal'' magnetoresistance material (La1-xCaxMnO3) was obtained for the first time through magnetization and resistivity measurements over a broad range of temperatures and concentrations. Near x = 0.50, the ground state changes from a ferromagnetic (FM) conductor to an antiferromagnetic (AFM) insulator, leading to a strongly first order AFM transition with supercooling of similar to 30% T-N at x = 0.50. An unexpectedly large magnetoresistance is seen at low temperatures in the FM phase, and is largely attributed to unusual domain wall scattering.