A single crystal of ~Bi0.24Ca0.76!MnO3 has been extensively studied using both laboratory and synchrotron radiation x-ray scattering. Using x-ray techniques we can directly observe the formation of charge stripes associated with the low-temperature structural phase transition. Weak satellite peaks with a modulation wave vector q'(0.24, 0.24, 0) were observed below the transition temperature. These are associated with the charge ordering of Mn31 and Mn41 ions into charge ~and spin! stripes within the perovskite structure. Measurements of the temperature dependence of the intensity and width of the charge-ordering satellites over the temperature range 10–240 K were also completed. These demonstrate the first-order nature of the structural phase transition that accompanies the formation of charge and spin ordering. Measurements of the width of the charge-order satellites demonstrate that the correlation length of the charge order is long range at all temperatures, and in all directions, below the structural phase transition.
Physical Review B (Condensed Matter and Materials Physics) 59(18), pp.11687-11692