Some magnetic materials show hidden order phases, where the order parameters are not observed using conventional magnetic measurements. The hidden order phase transition is usually accompanied by changes in the bulk properties such as heat capacity, but identification and understanding the phases is very difficult when they cannot be observed microscopically.
This study focusses on the recently discovered rare-earth triangular-lattice magnet TmMgGaO4. Bulk measurements show that a phase transition occurs at low temperature, but this is the first study to look at the microscopic measurements. The researchers used neutron scattering and thermodynamic measurements to study the phase transitions and spin correlations of single crystals of TmMgGaO4.
They observed clearly in the elastic neutron diffraction patterns that the longitudinal component of the effective spins is dipolar. However, they also observed spin excitations that were not present in the elastic diffraction patterns, corresponding to the transverse components. Their calculations demonstrate that this behaviour can be described by a transverse field Ising model on the triangular lattice, with an intertwined dipolar and ferro-multipolar order.
Reproduced from DOI: 10.1038/s41467-019-12410-3
Related publication: “Intertwined dipolar and multipolar order in the triangular-lattice magnet TmMgGaO4.” Nat Commun 10, 4530 (2019).
Funding: Innovation Program of Shanghai Municipal Education Commission, the Ministry of Science and Technology of China, the National Key R&D Program of the MOST of China and Hong Kong’s Research Grants Council.
Authors: Y Shen, C Liu, Y Qin, S Shen (Fudan University), Y Li (Fudan University, University of California Santa Barbara), R Bewley (ISIS), A Schneidewind (Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ)), G Chen (The University of Hong Kong, Fudan University, Nanjing University), J Zhao (Fudan University, Nanjing University)