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Structural invariance upon antiferromagnetic ordering in geometrically frustrated swedenborgite, CaBaCo 2 Fe 2 O 7

2014; Wiley; Volume: 47; Issue: 6 Linguagem: Inglês

10.1107/s1600576714023528

1600-5767

Johannes Reim, Erik Rosén, W. Schweika, Martin Meven, Naëmi Leo, Dennis Meier, M. Fiebig, Marcus Schmidt, Chang‐Yang Kuo, T.-W. Pi, Zhiwei Hu, Martin Valldor,

Multiferroics and related materials

Centimetre-sized single crystals of high-quality CaBaCo 2 Fe 2 O 7 were synthesized by the optical floating zone technique. The metal-to-metal stoichiometry and oxygen content were confirmed by spectroscopy and thermal reduction experiments. The hexagonal symmetry P 6 3 mc (No. 186) well describes the powder X-ray and neutron diffraction as well as single-crystal neutron diffraction at all measured temperatures. This symmetry is also consistent with optical second harmonic generation data obtained between 10 and 295 K. However, a satisfactory structure description from single-crystal neutron diffraction data needs an oxygen split position. Specific heat, magnetic susceptibility and powder neutron diffraction data indicate a magnetic phase transition at T N = 159 K to an antiferromagnetic ground state, but with a persisting hexagonal symmetry and intrinsic geometric frustration.