Insights into nature of a magnetization plateau of 3d-4f coordination polymer [Dy2Cu2]n from a spin-1/2 Ising-Heisenberg orthogonal-dimer chain

Abstract

The ground state and magnetization process of an exactly solved spin-1/2 Ising-Heisenberg orthogonal-dimer chain with two different gyromagnetic factors of the Ising and Heisenberg spins are investigated in detail. It is shown that the investigated quantum spin chain exhibits up to seven possible ground states depending on a mutual interplay of the magnetic field, intra- and inter-dimer coupling constants. More specifically, the frustrated and modulated quantum antiferromagnetic phases are responsible in zero-temperature magnetization curves for a zero magnetization plateau. The intermediate 1/11- and 5/11-plateaus emerge due to the frustrated and modulated quantum ferrimagnetic phases, while the intermediate 9/11- and 10/11-plateaus can be attributed to the quantum and classical ferrimagnetic phases. It is conjectured that the magnetization plateau experimentally observed in a high-field magnetization curve of 3d-4f heterobimetallic coordination polymer [{Dy(hfac)2(CH3OH)}2{Cu(dmg)(Hdmg)}2]n (H2dmg = dimethylglyoxime; Hhfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dione) could be attributed to the classical and quantum ferrimagnetic phases.

Ground State, Magnetization Process and Bipartite Quantum Entanglement of a Spin-1/2 Ising–Heisenberg Model on Planar Lattices of Interconnected Trigonal Bipyramids

“…The investigations brought a deeper insight into the thermal and magnetic-field-driven changes of the phenomenon [36][37][38][39][40][41][42][43], the impact of the model's parameters on the phenomenon [36,[39][40][41][42][43][44][45], as well as the evolution of the phenomenon near and above second-order (continuous) phase transitions [44,45] without any artefacts arising from approximations. Despite their simplicity and the general opinion that the simpler mixed-spin Ising-Heisenberg systems involving isolated local quantum correlations are artificial models, some of the results were in a very good correspondence with ones obtained for more complex Heisenberg counterparts [40] and also with experiments [38,46,47].…”

Insight into ground-state spin arrangement and bipartite entanglement of the polymeric coordination compound [Dy$_2$Cu$_2$]$_n$ through the symmetric spin-1/2 Ising-Heisenberg orthogonal-dimer chain

“…It is possible to do so because the Dy 3+ ions represent Kramers ions with the ground-state multiplet 6 H 15/2 which is a subject of strong crystal-field splitting into eight well separated Kramers doublets [33,34], even though two different types of the oximate O-N bridges are realized between Cu 2+ and Dy 3+ ions in the real [CuDy 2 Cu] cell [23]. Our recent study [30], providing a satisfactory theoretical fit of the magnetization data reported for [Dy 2 Cu 2 ] n at the temperature T = 0.5 K, is the convincing evidence for this. The magnetic structure of the corresponding spin-1/2 Ising-Heisenberg orthogonal-dimer chain, in which the Ising spins σ correspond to the Dy 3+ magnetic ions, the Heisenberg spins S correspond to the Cu 2+ magnetic ions.…”

“…In the present paper we build on findings in the recent article [30]. Taking into account the values of interaction coupling constants and gyromagnetic factors of spins fitted from magnetization data of [Dy 2 Cu 2 ] n , we theoretically examine a possible bipartite entanglement within Cu 2+ -Cu 2+ dimers in this polymer through the symmetric version of the isotropic spin-1/2 Ising-Heisenberg orthogonal-dimer chain.…”

“…Indeed, [Dy 2 Cu 2 ] n is formed by regularly alternating highly anisotropic dinuclear units of Dy 3+ ions, which can be theoretically described by the spin-1/2 Ising dimers, and roughly orthogonal almost isotropic dinuclear units of Cu 2+ ions, which can be approximated by the isotropic spin-1/2 Heisenberg dimers. Thanks to its rigorous solution, the spin-1/2 Ising-Heisenberg orthogonal-dimer chain and its extended versions are an excellent playground for theoretical investigation many intriguing magnetic properties arising from quantum correlations such as anomalous low-temperature thermodynamics [26][27][28] and enhanced magnetocaloric effect [26] near critical fields, fractional magnetization plateaus in the magnetization process [26,29,30], as well as bipartite entanglement within the Heisenberg dimers [27,29]. Moreover, it provides a fairly satisfactory theoretical fit for experimental magnetization data reported for the real polymeric compound [Dy 2 Cu 2 ] n at the temperature T = 0.5 K assuming the specific set of model's parameters [30].…”

“…The mixing angle ϕ, determining probability amplitudes of these states, is defined through the formula tan(2ϕ) = J H / J I σ z T,i − σ z T,i+1 . Referring to the most satisfactory theoretical fit of the experimental magnetization data for [Dy 2 Cu 2 ] n discussed in the recent article [30], the parameter set occurring in the cluster Hamiltonian (2) and its eigenvalues (3a)-(3d) will be hereafter fixed to the following specific values:…”