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Magnons and phonons are fundamental quasiparticles in a solid and can be coupled together to form a hybrid quasi-particle. However, detailed experimental studies on the underlying Hamiltonian of this particle are rare for actual materials. Moreover, the anharmonicity of such magnetoelastic excitations remains largely unexplored, although it is essential for a proper understanding of their diverse thermodynamic behaviour and intrinsic zero-temperature decay. Here we show that in non-collinear antiferromagnets, a strong magnon phonon coupling can significantly enhance the anharmonicity, resulting in the creation of magnetoelastic excitations and their spontaneous decay. By measuring the spin waves over the full Brillouin zone and carrying out anharmonic spin wave calculations using a Hamiltonian with an explicit magnon phonon coupling, we have identified a hybrid magnetoelastic mode in (Y,Lu)MnO $_{3}$ and quantified its decay rate and the exchange-striction coupling termrequired to produce it.

Journal Articles

OECD/NEA expert group on uncertainty analysis for criticality safety assessment; Current activities

Ivanova, T.*; Fernex, F.*; Kolbe, E.*; Vasiliev, A.*; Lee, G. S.*; Woo, S. W.*; Mennerdahl, D.*; Nagaya, Yasunobu; Neuber, J. C.*; Hoefer, A.*; et al.

Proceedings of International Conference on Physics of Reactors; Advances in Reactor Physics to Power the Nuclear Renaissance (PHYSOR 2010) (CD-ROM), 15 Pages, 2010/05

The expert group (EG) on Uncertainty Analysis for Criticality Safety Assessment (UACSA) was established within the OECD/NEA Working Party on Nuclear Criticality Safety in December 2007 to promote exchange of information on related topics; compare methods and software tools for uncertainty analysis; test their performance; and assist in selection/development of safe and efficient methodologies for validation of criticality computations. At the current stage, the work of the group is focused on approaches for validation of criticality calculations. With the diversity of the approaches to validate criticality calculations, a thorough description of each approach and assessment of its performance is useful to the criticality safety community. Developers, existing and potential practitioners as well as reviewers of assessments using those approaches should benefit from this effort. Exercise Phase I was conducted in order to illustrate predicting capabilities of criticality validation approaches, which include similarity assessment, definition of $k_mathit{eff}$ bias and bias uncertainty, and selection of benchmarks. The approaches and results of the exercises will be thoroughly documented in a pending state-of-the-art report from the EG. This paper provides an overview of current and future activities for the EG, a summary of the participant-contributed validation approaches, and a synthesis of the results for the exercises.

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In-situ neutron diffraction study of serration-involved ultra-cryogenic deformation behavior at 15 K

Competitive strengthening between dislocation slip and twinning in cast-wrought and additively manufactured CrCoNi medium entropy alloys

Multiple deformation scheme in direct energy deposited CoCrNi medium entropy alloy at 210K

Effect of the difference in strength of hard and soft components on the synergetic strengthening of layered materials

Comparison of dislocation density, twin fault probability, and stacking fault energy between CrCoNi and CrCoNiFe medium entropy alloys deformed at 293 and 140K

On the phase transformation and dynamic stress-strain partitioning of ferrous medium-entropy alloy using experimentation and finite element method

Stacking fault energy analyses of additively manufactured stainless steel 316L and CrCoNi medium entropy alloy using in situ neutron diffraction

Plastic anisotropy and deformation-induced phase transformation of additive manufactured stainless steel

Synergetic strengthening of layered steel sheet investigated using an neutron diffraction tensile test

neutron diffraction study of phase stress evolution in a ferrous medium-entropy alloy under low-temperature tensile loading

Residual stresses in steel rod with collar formed by partial diameter-enlarging technique

Spontaneous decays of magneto-elastic excitations in non-collinear antiferromagnet (Y,Lu)MnO $_{3}$

OECD/NEA expert group on uncertainty analysis for criticality safety assessment; Current activities