Charge ordering and structural distortions at low temperature inLa2−2xSr1+2x

In this paper we present x-ray scattering results of charge and orbital ordering in the bilayer manganite\udLa222xSr112xMn2O7 with doping levels x50.5 and x50.475. Using high-energy x-ray scattering, the structural\udmodulation due to the Jahn-Teller ordering and the charge ordering due to the Mn31/Mn41 pattern have\udbeen measured. Both the x50.5 and x50.475 samples are found to display charge and Jahn-Teller order. We\udhave confirmed that the wave vectors of the Jahn-Teller order, charge order, and orbital order are QW\ud5(0.25,0.25,0), QW\ud5(0.5,0.5,0) and QW\ud5(0.25,0.25,0). The origin of these has been confirmed by resonant\udx-ray scattering in the vicinity of the Mn K edge using polarization analysis. Contrary to previous studies, the\udJahn-Teller order is found to be not reentrant, but is found to reduce in intensity at temperatures below 140 K\udfor both samples. Charge ordering was also detected in the x50.5 sample below this temperature