Evidence of Orbital Ordering in Jahn-Teller Undistorted LaSr$_{2}$Mn$_{2}$O$_{7}$

S. B. Wilkins; N. Stojic; T. A. W. Beale; N. Binggeli; P. Bencok; S. Stanescu; J. F. Mitchell; P. Abbamonte; P. D. Hatton; M. Altarelli

arXiv · cond-mat/0412435

Evidence of Orbital Ordering in Jahn-Teller Undistorted LaSr$_{2}$Mn$_{2}$O$_{7}$

S. B. Wilkins·N. Stojic·T. A. W. Beale·N. Binggeli·P. Bencok·S. Stanescu·J. F. Mitchell·P. Abbamonte·P. D. Hatton·M. Altarelli

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Abstract

Resonant soft x-ray diffraction has been used to probe the temperature dependent orbital and magnetic structure of $\mathrm{LaSr_{2}Mn_{2}O_7}$. Previous crystallographic studies have shown that this material has almost no MnO$_{6}$ oxygen displacement due to Jahn-Teller distortions at low temperatures. Within the low-temperature A-type antiferromagnetic phase, we found strong intensity at the $({1/4},{1/4},0)$ orbital and $LaSr_{2}Mn_{2}O_7$ magnetic reflections. This shows that even in the near absence of Jahn-Teller distortion, this compound is strongly orbitally ordered. A fit to the Mn $L$-edge resonance spectra demonstrates the presence of orbital ordering of the Mn$^{3+}$ ions with virtually no Jahn-Teller crystal field in addition to possible Mn$^{3+}$ and Mn$^{2+}$~like valence fluctuations.

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S. B. Wilkins, N. Stojic, T. A. W. Beale, N. Binggeli, P. Bencok, S. Stanescu, J. F. Mitchell, P. Abbamonte, P. D. Hatton, M. Altarelli. 2006-06-03. Evidence of Orbital Ordering in Jahn-Teller Undistorted LaSr$_{2}$Mn$_{2}$O$_{7}$. https://arxiv.org/abs/cond-mat/0412435

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