- Milan Klicpera: Rare-earth A2B2O7 oxides: structural and magnetic properties
- 23. 11. 2022, 14:10
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Cubic A2B2O7 oxides with A standing for a rare-earth element and B for a transition or main block metal have been systematically studied for their frequently exotic crystallographic and electronic properties. Diverse ground states, magnetic structures and predicted exciting electronic, magnetic and even topological properties originating from a competition between electron-electron correlations and spin-orbit coupling have been reported . The geometrical frustration of magnetic moments residing on the A and/or B crystallographic positions offer a playground for scientific investigations as well.
A2B2O7 compounds in general crystallize either in a pyrochlore structure (F d -3 m, 227), defect-fluorite structure (F m -3 m, 225) or a low-symmetry monoclinic structure (P 1 1 21, 2 ) at ambient pressure. The pyrochlore structure represents one of the canonical examples for a structure where a unique ground state is difficult to achieve for a system of magnetically coupled moments as demonstrated on a number of compounds [1,3,4]. The fluorite structure is another example of a geometrically frustrated lattice, due to the fcc lattice of cations. However, the rare-earth/transition metal octahedra are edge-, not vertex-sharing leading to a different exchange pathway type and thus different magnetic exchanges. Moreover, the diluted magnetic lattice (complete A/B disorder on the 4a position) is bound to have a great impact on the ground state of A2B2O7 compounds as well.
The overview on our previous and recent results on A2B2O7 compounds will be presented. Recently, we focused on synthesis and characterization of single crystals of A2Ir2O7 pyrochlores, crystallographic properties of A2Zr2O7 zirconates, and transition between structure types in Er2(Ti,Zr)2O7 series.
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