Yb delafossites: unique exchange frustration of 4f spin 1/2 moments on a perfect triangular lattice

Abstract

While the Heisenberg model for magnetic Mott insulators on planar lattice structures is comparatively well understood in the case of transition metal ions, the intrinsic spin-orbit entanglement of 4f magnetic ions on such lattices shows fascinating new physics largely due to corresponding strong anisotropies both in their single-ion and their exchange properties. We show here that the Yb delafossites, containing perfect magnetic Yb${}^{3+}$ triangular lattice planes with pseudospin $s=1/2$ at low temperatures, are an ideal platform to study these new phenomena. Competing frustrated interactions may lead to an absence of magnetic order associated to a gapless spin liquid ground state with a huge linear specific heat exceeding that of many heavy fermions, whereas the application of a magnetic field induces anisotropic magnetic order with successive transitions into different long ranged ordered structures. In this comparative study, we discuss our experimental findings in terms of a unified crystal-field and exchange model. We combine electron paramagnetic resonance (EPR) experiments and results from neutron scattering with measurements of the magnetic susceptibility, isothermal magnetization up to full polarization, and specific heat to determine the relevant model parameters. The impact of the crystal field is discussed as well as the symmetry-compatible form of the exchange tensor, and we give explicit expressions for the anisotropic g factor, the temperature dependence of the susceptibility, the exchange-narrowed EPR linewidth and the saturation field.

20 pages, 7 figures, to appear in Physical Review B

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• Synthesis and Anisotropic Magnetism in Quantum Spin Liquid Candidates $A$YbSe${}_2$ ($A$ = K and Rb)
• Systematic extraction of crystal electric-field effects and quantum magnetic model parameters in triangular rare-earth magnets
• Stripe-yz magnetic order in the triangular-lattice antiferromagnet KCeS2
• Rare-Earth Chalcogenides: An Inspiring Playground For Exploring Frustrated Magnetism
• Diluting a triangular-lattice spin liquid: Synthesis and characterization of NaYb${}_{1-x}$Lu${}_x$S${}_2$ single crystals
• Tracking the evolution from isolated dimers to many-body entanglement in NaLu${}_x$Yb${}_{1-x}$Se${}_2$
• Nearly-Resonant Crystalline-Phononic Coupling in Quantum Spin Liquid Candidate CsYbSe${}_2$
• Stripe magnetic order and field-induced quantum criticality in the perfect triangular-lattice antiferromagnet CsCeSe${}_2$
• Excitation Spectrum and Spin Hamiltonian of the Frustrated Quantum Ising Magnet Pr${}_3$BWO${}_9$
• Role of alkaline metal in the rare-earth triangular antiferromagnet KYbO${}_2$
• Deriving quantum spin model for a zigzag-chain ytterbium magnet with anisotropic exchange interactions
• Quantifying uncertainties in crystal electric field Hamiltonian fits to neutron data
• Traversing the pyrochlore stability diagram; microwave-assisted synthesis and discovery of mixed B-site Ln${}_2$InSbO${}_7$ family
• Anisotropic magnetism and spin fluctuations in the triangular-lattice spin-liquid candidate NaYbSe${}_2$: a single-crystal ${}^{23}$Na and ${}^{77}$Se NMR study
• Field-driven transition from quantum spin liquid to magnetic order in triangular-lattice antiferromagnets
• Finite Temperature Magnetism in the Triangular Lattice Antiferromagnet KErTe2
• Electron spin resonance study on the 4f honeycomb quantum magnet YbCl3
• Magnetic field-temperature phase diagram of spin-1/2 triangular lattice antiferromagnet KYbSe${}_2$
• Cluster glass behavior and magnetocaloric effect in the hexagonal polymorph of disordered Ce${}_2$PdGe${}_3$
• Magnetic anisotropy and dipolar interactions in the frustrated triangular-lattice magnet NaGdS_2