Thermally induced rotation of3dorbital stripes inPr(Sr0.1Ca0.9)2Mn2O7

Abstract

We have investigated orbital ordering in the bilayer manganite, $\text{Pr}{({\text{Sr}}_{0.1}{\text{Ca}}_{0.9})}_{2}{\text{Mn}}_{2}{\text{O}}_{7}$, using synchrotron x-ray diffraction techniques, in particular resonant soft x-ray diffraction. Diffraction signals are observed at $(0,\frac{1}{2},0)$ above 300 K and $(\frac{1}{2},0,0)$ below 300 K, corresponding to orbital stripes along the $a$ and $b$ axes, respectively. The previously observed transition at 300 K is evidence of a rotation of the orientation of the $3d$ orbital stripes. Large resonances of the orbital signals are observed at the $\text{Mn}\text{ }L$ edges, with a complex dependence on incident photon energy indicative of a weakly Jahn-Teller distorted system. A structural transition observed at 92 K is found not to involve a further change in the orbital order.