Andrew Boothroyd

Abstract:

In this paper we present x-ray scattering results of charge and orbital ordering in the bilayer manganite La2−2xSr1+2xMn2O7 with doping levels x = 0.5 and x = 0.475. Using high-energy x-ray scattering, the structural modulation due to the Jahn-Teller ordering and the charge ordering due to the Mn3+/Mn4+ pattern have been measured. Both the x = 0.5 and x = 0.475 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 (Formula presented), (Formula presented) and (Formula presented). 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 x = 0.5 sample below this temperature. © 2003 The American Physical Society.