Elastic and anelastic anomalies associated with the antiferromagnetic ordering transition in wüstite, FexO

Autor(en)

Zhiying Zhang, Nathan Church, Sophie-Charlotte Lappe, Marius Reinecker, Armin Fuith, Paul J. Saines, Richard J. Harrison, Wilfried Schranz, Michael Allan Carpenter

Abstrakt

The elastic and anelastic properties of three different samples of FexO have been determined in the frequency range 0.1-2 MHz by resonant ultrasound spectroscopy and in the range 0.1-50 Hz by dynamic mechanical analysis in order to characterize ferroelastic aspects of the magnetic ordering transition at T-N similar to 195 K. No evidence was found of separate structural and magnetic transitions but softening of the shear modulus was consistent with the involvement of bilinear coupling, lambda(e4q), between a symmetry-breaking strain, e(4), and a structural order parameter, q. Unlike a purely ferroelastic transition, however, C-44 does not go to zero at the critical temperature, T-c*, due to the intervention of the magnetic ordering at a higher temperature. The overall pattern of behaviour is nevertheless consistent with what would be expected for a system with separate structural and magnetic instabilities, linear-quadratic coupling between the structural (q) and magnetic (m) driving order parameters, lambda qm(2), and T-N > T-c*. Comparison with data from the literature appears to confirm the same pattern in MnO and NiO, with a smaller difference between T-N and T-c* in the former and a larger difference in the latter. Strong attenuation of acoustic resonances at high frequencies and a familiar pattern of attenuation at low frequencies suggest that twin walls in the rhombohedral phase have typical ferroelastic properties. Acoustic dissipation in the stability field of the cubic phase is tentatively attributed to anelastic relaxations of the defect ordered structure of non-stoichiometric wustite or of the interface between local regions of wustite and magnetite, with a rate controlling step determined by the diffusion of iron.

Organisation(en)

Physik Funktioneller Materialien

Externe Organisation(en)

University of Cambridge

Journal

Journal of Physics: Condensed Matter

Band

24

Anzahl der Seiten

13

ISSN

0953-8984

DOI

https://doi.org/10.1088/0953-8984/24/21/215404

Publikationsdatum

2012

Peer-reviewed

Ja

ÖFOS 2012

103015 Kondensierte Materie, 210006 Nanotechnologie, 103018 Materialphysik, 103029 Statistische Physik

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/c43ab668-a92b-4fe6-aeb8-e7a4f9509dc4