Abstract
The geometric frustration in a class of the mixed spin-1=2 and spin-S Ising-Heisenberg diamond chains is investigated by combining three exact analytical techniques: Kambe projection method, decoration-iteration transformation and transfer-matrix method. The ground state, the magnetization process and the specic heat as a function of the external magnetic eld are particularly examined for different strengths of the geometric frustration. It is shown that the increase of the Heisenberg spin value S raises the number of intermediate magnetization plateaux, which emerge in magnetization curves provided that the ground state is highly degenerate on behalf of a sufciently strong geometric frustration. On the other hand, all intermediate magnetization plateaux merge into a linear magnetization versus magnetic eld dependence in the limit of classical Heisenberg spin S ! 1. The enhanced magnetocaloric effect with cooling rate exceeding the one of paramagnetic salts is also detected when the disordered frustrated phase constitutes the ground state and the external magnetic eld is small enough.
Highlights
The quantum Heisenberg model with diamond chain topology has enjoyed a great scientific interest since two unusual tetramer-dimer and dimer-monomer phases were theoretically predicted by Takano et al [1] in the zero-field ground-state phase diagram of the spin-1/2 Heisenberg diamond chain as a result of the mutual interplay between quantum fluctuations and geometric frustration
Let us proceed to a discussion of the most interesting results obtained for the mixed spin-1/2 and spin-S Ising-Heisenberg diamond chain
Within the framework of this exact analytical approach, the ground-state phase diagrams and the magnetization process were examined depending on a strength of the geometric frustration, as well as, the quantum spin number S of the Heisenberg spins
Summary
The quantum Heisenberg model with diamond chain topology has enjoyed a great scientific interest since two unusual tetramer-dimer and dimer-monomer phases were theoretically predicted by Takano et al [1] in the zero-field ground-state phase diagram of the spin-1/2 Heisenberg diamond chain as a result of the mutual interplay between quantum fluctuations and geometric frustration. Motivated by this discovery, several other one-dimensional (1D) quantum spin models consisting of diamond-shaped units have been suggested and solved with the aim of bringing insight into a frustrated magnetism of diamond chain systems.
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