No abstract

Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. In this paper we present x-ray scattering results of charge and orbital ordering in the bilayer manganite La 2Ϫ2x Sr 1ϩ2x Mn 2 O 7 with doping levels xϭ0.5 and xϭ0.475. Using high-energy x-ray scattering, the structural modulation due to the Jahn-Teller ordering and the charge ordering due to the Mn 3ϩ /Mn 4ϩ pattern have been measured. Both the xϭ0.5 and xϭ0.475 samples are found to display charge and Jahn-Teller order. We have confirmed that the wave vectors of the Jahn-Teller order, charge order, and orbital order are Q ជ ϭ(0.25,0.25,0), Q ជ ϭ(0.5,0.5,0) and Q ជ ϭ(0.25,0.25,0). The origin of these has been confirmed by resonant x-ray scattering in the vicinity of the Mn K edge using polarization analysis. Contrary to previous studies, the Jahn-Teller order is found to be not reentrant, but is found to reduce in intensity at temperatures below 140 K for both samples. Charge ordering was also detected in the xϭ0.5 sample below this temperature.

Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. We present high resolution high energy and resonant x-ray diffraction results from La2−2xSr1+2xMn2O7 for x = 0.55, 0.575 and 0.60. These compounds show superlattice reflections at wavevectors of (h ± δ, k ± δ, l) and (h ± 2δ, k ± 2δ, l), arising from orbital ordering with associated Jahn-Teller distortions and charge ordering respectively. We observe a phase transition between the x = 0.55 and x = 0.575 doping levels. Samples with x = 0.55 display structural characteristics similar to those previously reported for x = 0.5. Compared to this, the long range order in samples with x = 0.55 and x = 0.6 have a distinct change in wavevector and correlation. We attribute this to a new orbital bi-stripe phase, accompanied by weak, frustrated, charge ordering. The observed azimuthal dependence of the orbital order reflections supports the model proposed for this new phase.