Direct Observation of Orbital Order in Manganites by MEM Charge-Density Study

Abstract
We have investigated the charge-density distribution of an antiferromagnetic bi-layered manganite, NdSr 2 Mn 2 O 7 , by the maximum entropy method (MEM) using the synchrotron X-ray powder data. The magnetic structure below T N =150 K is known to be a layered-type (A-type). We have found a significant change of the electron distribution around the Mn site below T N . Our observation indicates d x 2 - y 2 -orbital polarization in the A-type antiferromagnetic state.