Abstract
The ferrimagnetic spin-1/2 chain composed of alternating Ising and Heisenberg spins in an arbitrarily oriented magnetic field is exactly solved using the spin-rotation transformation and the transfer-matrix method. It is shown that the low-temperature magnetization process depends basically on a spatial orientation of the magnetic field. A sharp stepwise magnetization curve with a marked intermediate plateau, which emerges for the magnetic field applied along the easy-axis direction of the Ising spins, becomes smoother and the intermediate plateau shrinks if the external field is tilted from the easy-axis direction. The magnetization curve of a polycrystalline system is also calculated by performing powder averaging of the derived magnetization formula. The proposed spin-chain model brings an insight into high-field magnetization data of 3d-4f bimetallic polymeric compound Dy(NO_3)(DMSO)_2Cu(opba)(DMSO)_2, which provides an interesting experimental realization of the ferrimagnetic chain composed of two different but regularly alternating spin-1/2 magnetic ions Dy^{3+} and Cu^{2+} that are reasonably approximated by the notion of Ising and Heisenberg spins, respectively.
Highlights
Solved quantum spin chains belong to the most attracting issues to deal with in the condensed matter theory, because they are capable of providing a deeper understanding into many unconvential quantum cooperative phenomena [1]
The low-temperature magnetization curve of the investigated spin-chain model was scrupulously examined in the dependence on a spatial orientation of the applied magnetic field
It has been demonstrated that the magnetization curve becomes smoother, the intermediate plateau shrinks, and the total magnetization is reduced by quantum fluctuations as the external field deviates from the easy axis of the Ising spins
Summary
Solved quantum spin chains belong to the most attracting issues to deal with in the condensed matter theory, because they are capable of providing a deeper understanding into many unconvential quantum cooperative phenomena [1]. The Ising-Heisenberg chains have become helpful in providing the evidence for several novel and unexpected quantum states [2,3,4,5,6], fractional magnetization plateaus in the low-temperature magnetization process [4,5,6], enhanced magnetocaloric effect during the adiabatic demagnetization [5], thermal entanglement [7], etc It is, quite challenging to search for suitable experimental realizations of the Ising-Heisenberg chains testifying to the aforementioned theoretical findings, but only a few experimental systems satisfy a very specific requirement of a regular alternation of the Ising and Heisenberg spins.
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