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Entropy Driven Incommensurate Structures in the Frustrated Kagome Staircase Co3V2O8



Joel Helton, Nyrissa Rogado, Robert Cava, Jeffrey Lynn


Co3V2O8 features spin-3/2 moments arrayed on a kagome staircase lattice. A spin density wave with a continuously evolving propagation vector of ⃗k = (0, δ, 0), showing both incommensurate states and multiple commensurate lock-ins, is observed at temperatures above the ferromagnetic ground state. Previous work has suggested that this changing propagation vector could be driven by changes in exchange interactions due to Co atom displacements. We present a straightforward model showing that a Hamiltonian with competing (but temperature independent) interactions can semi-quantitatively reproduce this behavior using a mean field approximation. The spin density wave magnetic structures feature buckled kagome planes that are either ferromagnetically or antiferromagnetically ordered. Propagation vectors that differ from δ = 1/2 will have multiple different ways of arranging these ferromagnetic layers that have very similar energies. This classical stacking entropy appears to be crucial in stabilizing the temperature-dependent propagation vector.
Journal of Physics: Condensed Matter


kagome staircase lattice, spin density wave, incommensurate magnet, lock-in transitions, competing interactions and entropy


Helton, J. , Rogado, N. , Cava, R. and Lynn, J. (2024), Entropy Driven Incommensurate Structures in the Frustrated Kagome Staircase Co3V2O8, Journal of Physics: Condensed Matter, [online], 10.1088/1361-648X/ad266b, (Accessed April 19, 2024)
Created February 18, 2024, Updated March 12, 2024