Near-ideal molecule-based Haldane spin chain

Robert C Williams,Tom Lancaster,Martin R Lees,Andrew Ozarowski,Serena M Birnbaum,John Singleton,John A Schlueter,Zurab Guguchia,Stephen J Blundell,Jamie L Manson,T J Hicken ,F L Pratt ,Danielle Villa ,C Baines ,Xing Fan ,William P Blackmore ,B M Huddart ,S P M Curley ,David Voneshen ,Paul Goddard

doi:10.1103/physrevresearch.2.013082

Abstract

The Haldane chain is a quantum mechanical model of contemporary research interest due to its non-trivial topological properties and outstanding unanswered questions. Experimental progress is hindered by difficulties in finding real materials that support the model. By exploiting recent advances in the design of molecule-based materials, the authors build a new system which they show is a uniquely ideal real Haldane chain with a quantum critical point that can be accessed using low-field magnets.

Highlights

The intrachain Ni–Ni separation is c = 9.9783(2) Å, where the magnetic superexchange interaction J is mediated via the two iodine ions, and the linear configuration suggests AFM interactions according to the Goodenough-Kanamori rules [48,49,50]
The chains running parallel to c lie on the axes of fourfold rotational symmetry operators, which preclude the existence of rhombic single-ion anisotropy (SIA), and we expect the magnetic behavior of NiI2(3, 5-lut)4 to be described by the Hamiltonian in Eq (1)
We have shown that NiI2(3, 5-lut)4 is a realization of a S = 1 Heisenberg AFM 1D chain, with intrachain exchange coupling J = 17.5(2) K manifested by unique Ni–I · · · I–Ni magnetic couplings

Summary

Introduction

Molecule-based magnets have proved a highly successful avenue in achieving desired lowdimensional geometries [1,2,3]. Several classes of materials which host quantum-disordered nonmagnetic ground states can undergo magnetic field and pressure driven quantum phase transitions (QPTs), where the magnetic ground states. An important asset of molecule-based systems is the modest energy scale of their exchange interaction strengths, which makes their QPTs experimentally accessible, providing a vital opportunity to test the predictions of theory and simulations. Of note is that several of these halide containing materials rely on through-space magnetic couplings, i.e., two-halide exchange, 2643-1564/2020/2(1)/013082(15)

Methods

Results

Discussion

Conclusion