Abstract
We study the ground-state and finite-temperature magnetic properties of an interlayer frustrated J1 − J2 − Jc Heisenberg model on three-dimensional honeycomb lattice by employing the Schwinger boson mean-field theory, focusing on the low-energy physics in In3Cu2VO9. We find that with the increase of interlayer coupling Jc from 0 to 3.6 meV, the interlayer frustrated system transits from an antiferromagnetic (AFM) phase to a state with intralayer AFM order and interlayer disorder. This spin disordered phase explains not only the intralayer phase transition at TN = 38 K, but also the qualitative behaviors of the intermediate-temperature specific heat and magnetic susceptibility of In3Cu2VO9.
Highlights
Two-dimensional (2D) honeycomb lattice has low coordination number (Z = 3) and small spin number (S = 1/2), in which large quantum spin fluctuations are expected to drive the system into a low-dimensional antiferromagnet (AFM), or even exotic spin disorder or liquid phase.[1]
The experimental absence of AFM long-range order (LRO) is quite different from the results given by the first-principles electronic structure calculation: the next-nearest-neighbor (NNN) AFM coupling J2 and the nearest-neighbor (NN) intralayer AFM coupling J1 in honeycomb lattice In3Cu2VO9 satisfy J2/J1 < 0.21, suggesting that it should be AFM ordered.[4]
It is essential to explore the role of interlayer frustration in the ground state and estimate the approximate scope of the spin disorder or liquid phase in the J1-J2-Jc phase diagram
Summary
Moller et al synthesized a layered honeycomb copper oxide In3Cu2VO9 which meets these conditions and exhibits anomalous behaviors:[2] the specific heat of undoped In3Cu2VO9 has no AFM long-range order (LRO) and AFM transition until down to 2 K, except a small strange cusp in magnetic susceptibility around T N = 38 K. Similar phase diagram was obtained by Yan et al.[3] its magnetic susceptibility and specific heat exhibited a very broad bump over wide temperature range from 50 K to 300 K,3 implying a possibility of spin disorder or liquid phase. We employ the Schwinger boson mean-field theory (SBMFT) to study the ground-state and finite-temperature properties in In3Cu2VO9.6 We show that its anomalous magnetic properties are associated with a spin disordered phase, in which the intralayer spins are ordered and interlayer spins are disordered
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