Abstract
Magnetic and magnetocaloric properties of a spin-1 Heisenberg diamond cluster with two different coupling constants are investigated with the help of an exact diagonalization based on the Kambe’s method, which employs a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster. It is shown that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which are manifested in low-temperature magnetization curves as intermediate plateaus at 1/4, 1/2, and 3/4 of the saturation magnetization. In addition, the spin-1 Heisenberg diamond cluster may also exhibit an enhanced magnetocaloric effect, which may be relevant for a low-temperature refrigeration achieved through the adiabatic demagnetization. It is evidenced that the spin-1 Heisenberg diamond cluster with the antiferromagnetic coupling constants J1/kB = 41.4 K and J2/kB = 9.2 K satisfactorily reproduces a low-temperature magnetization curve recorded for the tetranuclear nickel complex [Ni4(μ-CO3)2(aetpy)8](ClO4)4 (aetpy = 2-aminoethyl-pyridine) including a size and position of intermediate plateaus detected at 1/2 and 3/4 of the saturation magnetization. A microscopic nature of fractional magnetization plateaus observed experimentally is clarified and interpreted in terms of valence-bond crystal with either a single or double valence bond. It is suggested that this frustrated magnetic molecule can provide a prospective cryogenic coolant with the maximal isothermal entropy change −ΔSM=10.6 J·K−1·kg−1 in a temperature range below 2.3 K.
Highlights
Molecular-based magnetic materials have attracted a considerable research interest over the past few decades because they provide perspective building blocks for a development of new generation of nanoscale devices with a broad application potential [1,2,3,4]
We have investigated in detail magnetic and magnetocaloric properties of the spin-1 Heisenberg diamond cluster with two different coupling constants through an exact diagonalization based on the Kambe’s method, which takes advantage of a local conservation of composite spins formed by spin-1 entities located in opposite corners of a diamond spin cluster
It has been verified that the spin-1 Heisenberg diamond cluster exhibits several intriguing quantum ground states, which come to light in low-temperature magnetization curves as intermediate 1/4, 1/2, or 3/4-plateau depending on a specific choice of the interaction ratio and the magnetic field
Summary
Molecular-based magnetic materials have attracted a considerable research interest over the past few decades because they provide perspective building blocks for a development of new generation of nanoscale devices with a broad application potential [1,2,3,4]. Small magnetic molecules composed a few exchange-coupled spin centers might, for instance, serve for the rational design of high-density storage devices [5] and various spintronic devices [6,7,8]. Another intriguing feature of a special class of molecular magnetic materials with an extremely slow magnetic relaxation, which are commonly referred to as single-molecule magnets, is their possible implementation for developing novel platform for a quantum computation and quantum information processing [9,10,11,12,13,14,15].
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