Chemical, Orbital and Spin Ordering Complex Perovskites

Patrick M. Woodward
Department of Chemistry
Ohio State University

In this talk I will explore the structures and properties of two families of complex
perovskites, A2MnRuO6 (A = Sr, Ca, La) perovskites display a variety of interesting
properties. Despite the lack of long range Mn/Ru chemical order, long range magnetic
order sets in above 200 K and orbital order is realized for certain combinations of A-site
cations. Octahedral tilting distortions can be used to disrupt the orbital ordering and drive
the magnetic ordering from antiferromagnetic to ferromagnetic. In NaRMnWO6 (R = La,
Nd, Tb) exhibit simultaneous layered Na/Ln ordering and rock salt Mg/W ordering. The
unusual observation of layered ordering A-site cations is stabilized by second order Jahn-
Teller distortions of the W6+ cations. Magnetic ordering of the Mn2+ ions couples with
magnetic ordering of Ln cation layers to produce interesting sequences of phase
transitions. Electron microscopy studies of the related composition, NaLaMgWO6 show
a remarkable periodic nanoscale phase separation.

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