Spontaneous decays of magneto-elastic excitations in non-collinear antiferromagnet (Y/Lu)MnO3

마그논과 포논은 각각 자기 및 격자 시스템의 준입자이다. 본 연구는 스핀이 비동일선상 정렬을 하는 자성체의 경우 마그논과 포논이 강하게 결합하여 자기-탄성(magneto-elastic) 준입자의 발생 및 붕괴를 유발함을 보여준다. 연구진은 비탄성 중성자 산란 실험과 마그논 포논 결합을 고려한 이론계산을 통하여 (Y/Lu)MnO3에서 자기-탄성 준입자를 확인하였고 결합 메커니즘과 붕괴율을 규명하였다.

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)MnO3 and quantified its decay rate and the exchange-striction coupling term required to produce it.

참여 연구원: 오주성, 심하성, 박제근

Nature Communications 7, Article number: 13146 (2016)
doi:10.1038/ncomms13146

https://www.nature.com/articles/ncomms13146
https://www.ibs.re.kr/cop/bbs/BBSMSTR_000000000735/selectBoardArticle.do?nttId=13669&pageIndex=1&searchCnd=&searchWrd=