Ferrimagnetic spin-1/2 chain of alternating Ising and Heisenberg spins in arbitrarily oriented magnetic field

TL;DR

This paper exactly solves a ferrimagnetic spin-1/2 chain model with alternating Ising and Heisenberg spins in any magnetic field orientation, revealing how magnetization behavior depends on field direction and applying findings to real materials.

Contribution

It introduces an exact solution for the ferrimagnetic chain with arbitrary field orientation, linking theoretical results to experimental high-field magnetization data of a specific compound.

Findings

Magnetization depends on magnetic field orientation.

Intermediate plateau shrinks when field is tilted.

Model explains high-field magnetization in a Dy-Cu compound.

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.