Static and dynamical properties of the spin-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mfrac><mml:mn>5</mml:mn><mml:mn>2</mml:mn></mml:mfrac></mml:math> nearly ideal triangular lattice antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Ba</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">MnSb</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>9</mml:mn></mml:msub></mml:math>
Mingfang Shu, Weicen Dong, Jinlong Jiao, Jiangtao Wu, Gaoting Lin, Yoshitomo Kamiya, Tao Hong, Huibo Cao, Masaaki Matsuda, Wei Tian, Songxue Chi, G. Ehlers, Zhongwen Ouyang, Hongwei Chen, Youming Zou, Zhe Qu, Qing Huang, Haidong Zhou, Jie Ma
Abstract
We study the ground state and spin excitations in ${\mathrm{Ba}}_{3}{\mathrm{MnSb}}_{2}{\mathrm{O}}_{9}$, an easy-plane $S=5/2$ triangular lattice antiferromagnet. By combining single-crystal neutron scattering, electric spin resonance (ESR), and spin wave calculations, we determine the frustrated quasi-two-dimensional spin Hamiltonian parameters describing the material. While the material has a slight monoclinic structural distortion, which could allow for isosceles-triangular exchanges and biaxial anisotropy by symmetry, we observe no deviation from the behavior expected for spin waves in the in-plane ${120}^{\ensuremath{\circ}}$ state. Even the easy-plane anisotropy is so small that it can only be detected by ESR in our study. In conjunction with the quasi-two-dimensionality, our study establishes that ${\mathrm{Ba}}_{3}{\mathrm{MnSb}}_{2}{\mathrm{O}}_{9}$ is a nearly ideal triangular lattice antiferromagnet with the quasiclassical spin $S=5/2$, which suggests that it has the potential for an experimental study of $Z$- or ${Z}_{2}$-vortex excitations.