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

摘要: The elastic and anelastic properties of three different samples FexO have been determined in the frequency range 0.1?2?MHz by resonant ultrasound spectroscopy 0.1?50?Hz dynamic mechanical analysis order to characterize ferroelastic aspects magnetic ordering transition at TN???195?K. No evidence was found separate structural transitions but softening shear modulus consistent with involvement bilinear coupling, ?e4q, between a symmetry-breaking strain, e4, parameter, q. Unlike purely transition, however, C44 does not go zero critical temperature, , due intervention higher temperature. overall pattern behaviour is nevertheless what would be expected for system instabilities, linear?quadratic coupling (q) (m) driving parameters, ?qm2, . Comparison data from literature appears confirm same MnO NiO, smaller difference TN former larger latter. Strong attenuation acoustic resonances high frequencies familiar low suggest that twin walls rhombohedral phase typical properties. Acoustic dissipation stability field cubic tentatively attributed relaxations defect ordered structure non-stoichiometric w?stite or interface local regions magnetite, rate controlling step diffusion iron.