| Evidence of Orbital Ordering in Jahn-Teller Undistorted LaSr$_{2}$Mn$_{2}$O$_{7}$ (2004) | |||||||||||||
Abstract | |||||||||||||
| Resonant soft x-ray diffraction has been used to probe the orbital and magnetic structure of LaSr$_2$Mn$_2$O$_7$ at low temperatures. Previous crystallographic studies have shown that this material has almost no MnO$_{6}$ oxygen displacements due to Jahn-Teller distortions. Within the A-type antiferromagnetic phase we found strong intensity at the (0.25 0.25 0) orbital and (001) magnetic reflections. This shows that even in the absence of Jahn-Teller distortions, this compound is strongly orbitally ordered. The fit to the energy dependence of the orbital order reflection shows the absence of the Jahn-Teller distortion. Fitting of the Mn $L$-edge resonance spectra demonstrates the presence of orbital ordering of the Mn$^{3+}$ ions within an almost cubic crystal field in addition to valence fluctuations of a Mn$^{3+}$ and Mn$^{2+}$ type. | |||||||||||||
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