Stripe-yz magnetic order in the triangular-lattice antiferromagnet KCeS₂

Abstract

Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO2, NaYbS2, and NaYbSe2, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeS2 exhibits magnetic order below T N = 400 mK, which was so far identified only in thermodynamic measurements. Here we reveal the magnetic structure of this long-range ordered phase using magnetic neutron diffraction. We show that it represents the so-called ‘stripe-yz’ type of antiferromagnetic order with spins lying approximately in the triangular-lattice planes orthogonal to the nearest-neighbor Ce–Ce bonds. No structural lattice distortions are revealed below T N, indicating that the triangular lattice of Ce3+ ions remains geometrically perfect down to the lowest temperatures. We propose an effective Hamiltonian for KCeS2, based on a fit to the results of ab initio calculations, and demonstrate that its magnetic ground state matches the experimental spin structure.

The Shanghai alliance of multilingual researchers: Fudan University, Tongji University, Shanghai University of Finance and Economics, and Shanghai International Studies University, China

“…This family of materials crystallizes into a delafossite structure with space group R-3m or P 6 3 /mmc, while the trivalent R 3+ ions reside in a local environment with D 3d symmetry. Tremendous investigations on Yb 3+ - [28][29][30][31][32][33][34][35][36][37], Er 3+ - [38][39][40], and Ce 3+based [41][42][43] 112-family magnets have been reported, including massive precise knowledge of the CEF excitations in them [44][45][46][47][48][49][50][51]. However, while the majority of studies focus on materials in which the triangular lattice is formed by Kramers ions in ARCh 2 family, research on compounds featuring non-Kramers ions is rather limited.…”

Stripe order and spin dynamics in the triangular-lattice antiferromagnet KErSe2 : A single-crystal study with a theoretical description

“…Conversely, the Cebased counterpart ACeCh 2 (A = alkali metal) compounds exhibit diverse magnetic properties. Although KCeO 2 and KCeS 2 both develop long-range magnetic orders at low temperatures, as suggested by the specific-heat measurements and spin-wavelike magnetic excitations [26][27][28][29], RbCeO 2 , on the contrary, enters a quantum-disordered ground state [30].…”

Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

“…However, among all 4f elements, the Ce 3+ ion is perhaps the only lanthanide where DFT models are capable of producing some single-particle properties reliably, in particular spin densities. In our previous studies of both metallic and insulating Ce-based systems like CeB 6 [14] and KCeS 2 [54], we have shown that the accuracy of DFT in predicting the spin density distribution within the DFT/PBE/PAW framework compared to CASSCF-level calculations is surprisingly high.…”