Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 32: Correlated Electrons: Poster Session

TT 32.32: Poster

Donnerstag, 28. Februar 2008, 14:00–18:00, Poster B

Resonant diffraction from charge and spin ordering in La_1.5Sr_0.5CoO₄ — •Christian Schüßler-Langeheine¹, Matthias Cwik¹, Chun Fu Chang¹, Hsueh-Hung Wu^1,2, Marcel Buchholz¹, Zhiwei Hu¹, Thomas Willers¹, Enrico Schierle³, Ralf Feyerherm³, Detlef Schmitz³, Mohammed Benomar¹, Markus Braden¹, and L. Hao Tjeng¹ — ¹II. Physikalisches Institut, Universität zu Köln — ²NSRRC, Taiwan — ³HMI c/o BESSY

Cobalt oxides are particularly interesting materials because of the different possible spin states of the Co³⁺ ion, which can occur in the low-spin, intermediate-spin or high-spin state. This adds another degree of freedom to charge, spin and orbital occupation of other transition metal ions. For La_1.5Sr_0.5CoO₄ commensurate charge and spin order was reported with a very unusual suppression of static magnetic ordering.

We studied this system using resonant diffraction at the Co K and L_2,3 resonance in order to obtain information about both charge and spin ordering. We find a pronounced pattern of incommensurate charge ordering not observed by neutron diffraction. From the magnetic scattering data we are able to determine the ordered orbital momentum and find indications for a more complex magnetic ordering than discussed so far.

Supported by the DFG through SFB 608 and by the BMBF.