Phase Transitions of the Magnetoelectric A2NiMoO6 (A = Ba, Sr) and Ca2NiWO6 by Neutron Diffraction

• The magnetic ferroelectric double perovskites A2NiMoO6 (A = Ba, Sr), and Ca2NiWO6have been characterised using neutron powder diffraction (NPD) data. The Ba2NiMoO6compound has previously been reported in cubic or hexagonal symmetry which led to investigationof polymorphism. High temperature NPD data of the Sr2NiMoO6 compoundindicates a continuous structural phase transition from tetragonal to cubic symmetry atapproximately 550 K. The reduction in symmetry is linked to spontaneous polarizationallowing the structural perturbation to be described as an improper ferroelectric phasetransition. The Ca2NiWO6 compound shows similar behaviour as Sr2NiMoO6 above700 K, possibly P21/n→(I2/m)→14/m→Fm-3m.

Ämnesord

NATURVETENSKAP  -- Kemi -- Oorganisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Inorganic Chemistry (hsv//eng)

Nyckelord

Phase Transition

Double perovskite

Magnetoelectric

Neutron Diffraction

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