This title appears in the Scientific Report : 2020 

Partial Up-Up-Down Order with the Continuously Distributed Order Parameter in the Triangular Antiferromagnet TmMgGaO 4
Li, Yuesheng (Corresponding author)
Bachus, Sebastian / Deng, Hao / Schmidt, Wolfgang / Thoma, Henrik / Hutanu, Vladimir / Tokiwa, Yoshifumi / Tsirlin, Alexander A. / Gegenwart, Philipp
Streumethoden; PGI-4
Heinz Maier-Leibnitz Zentrum; MLZ
Streumethoden; JCNS-2
Physical review / X, 10 (2020) 1, S. 011007
College Park, Md. APS 2020
Journal Article
Materials and Processes for Energy and Transport Technologies
Quantum Condensed Matter: Magnetism, Superconductivity
Controlling Collective States
Jülich Centre for Neutron Research (JCNS)
Controlling Collective States
Please use the identifier: in citations.
Please use the identifier: in citations.
We show that frustrated quasidoublets without time-reversal symmetry can host highly unconventional magnetic structures with continuously distributed order parameters even in a single-phase crystal. Our study comprises a comprehensive thermodynamic and neutron diffraction investigation on the single crystal of TmMgGaO4, which entails non-Kramers Tm3+ ions arranged on a geometrically perfect triangular lattice. The crystal electric field randomness caused by the site-mixing disorder of the nonmagnetic Mg2+ and Ga3+ ions merges two lowest-lying crystal electric field singlets of Tm3+ into a ground-state quasidoublet. Well below Tc∼0.7  K, a small fraction of the antiferromagnetically coupled Tm3+ Ising quasidoublets with small inner gaps condense into two-dimensional up-up-down magnetic structures with continuously distributed order parameters, and give rise to the columnar magnetic neutron reflections below μ0Hc∼2.6  T, with highly anisotropic correlation lengths, ξab≥250a in the triangular plane and ξc<c/12 between the planes. The remaining fraction of the Tm3+ ions remain nonmagnetic at 0 T and become uniformly polarized by the applied longitudinal field at low temperatures. We argue that the similar model can be generally applied to other compounds of non-Kramers rare-earth ions with correlated ground-state quasidoublets.