Evidence for charge localization in the ferromagnetic phase ofLa1−xCaxMnO3from high real-space-resolution x-ray diffraction

S. J. L. Billinge, Th. Proffen, V. Petkov, J. L. Sarrao, S. Kycia
2000 Physical Review B (Condensed Matter)  
High real-space-resolution atomic pair distribution functions of La_(1-x)Ca_(x)MnO_3 (x=0.12, 0.25 and 0.33) have been measured using high-energy x-ray powder diffraction to study the size and shape of the MnO_6 octahedron as a function of temperature and doping. In the paramagnetic insulating phase we find evidence for three distinct bond-lengths ( 1.88, 1.95 and 2.15A) which we ascribe to Mn^4+-O, Mn^3+-O short and Mn^3+-O long bonds respectively. In the ferromagnetic metallic (FM) phase, for
more » ... lic (FM) phase, for x=0.33 and T=20K, we find a single Mn-O bond-length; however, as the metal-insulator transition is approached either by increasing T or decreasing x, intensity progressively appears around r=2.15 and in the region 1.8 - 1.9A suggesting the appearance of Mn^3+-O long bonds and short Mn^4+-O bonds. This is strong evidence that charge localized and delocalized phases coexist close to the metal-insulator transition in the FM phase.
doi:10.1103/physrevb.62.1203 fatcat:r3uvgdldx5cmvhipln2rt2iriu