Quasiparamagnetic ground state in the hyperhoneycomb lattice compound
Quasiparamagnetic ground state in the hyperhoneycomb lattice compound
In this study, we investigated the magnetic properties of , a hyperhoneycomb lattice-based material with a scheelite structure characterized by intrinsic antisite-disorder between sodium (Na) and ytterbium (Yb) ions. Through detailed magnetization measurements down to 400 mK, we found no evidence of long-range magnetic ordering. Analysis of the inverse susceptibility data using a modified Curie-Weiss law suggests that the ground state is best described as a Kramers doublet with 𝐽eff = 1/2. Analysis of the field dependence of the Schottky anomaly evident in the heat capacity data indicates a small finite energy gap in zero field, Δ(0)∼0.5K. Our findings were corroborated by muon spin relaxation (µSR) measurements, which indicated the presence of a dynamic magnetic state along with an Orbach process involving crystal electric field (CEF) levels below 20 K. Additionally, field-dependent thermal conductivity measurements displayed anomalies that, together with the magnetization and heat capacity data, suggest the excitation of the spins to higher energy levels for magnetic fields 𝐻≥ 2 T. Finally, a combination of density functional theory (DFT) and Monte Carlo simulations revealed that a combination of geometrical frustration and competing exchange interactions are responsible for the quasiparamagnetic ground state observed in this system.
(a) Lattice A, with the Yb atoms in green. (b) shows a schematic representation of the nearest and next-nearest neighbors in this lattice. The nearest neighbors are connected by a solid black line and the next-nearest neighbors by a dotted black line. J1 and J2, which are of opposing character, acts on Yb atoms arranged in a triangle, leading to a frustration. Lattice A has two nearest neighbors and four next-nearest neighbors. (c) The unit cell of lattice B. (d) A schematic diagram showing only the Yb atoms. The nearest and next-nearest neighbors are shown with a solid black line and a dotted black line, respectively. Lattice B has four nearest neighbors and eight next-nearest neighbors.
