Structural response to O*-O ' and magnetic transitions in orthorhombic perovskites

We present a temperature-dependent single-crystal x-ray-diffraction study of twinned orthorhombic perovskites La1-xCaxMnO3, for x=0.16 and x=0.25. These data show the evolution of the crystal structure from the ferromagnetic insulating state to the ferromagnetic metallic state. The data are modeled in space group Pnma with twin relations based on a distribution of the b axis over three perpendicular cubic axes. The twin model allows full structure determination in the presence of up to six twin fractions using the single-crystal x-ray-diffraction data.