Effective realization of random magnetic fields in compounds with large single-ion anisotropy

TL;DR

This paper demonstrates that large single-ion anisotropy in spin-1 systems can be effectively mapped to spin-1/2 systems with random magnetic fields, enabling experimental and theoretical studies of disorder effects on magnetic transport.

Contribution

It introduces a mapping from spin-1 systems with large anisotropy to spin-1/2 systems with random fields, supported by numerical validation in specific compounds.

Findings

Excellent agreement between spin-1 and spin-1/2 models for static properties

Effective models reproduce spin conductivity results

Realization in specific compounds enables experimental studies

Abstract

We show that spin $S=1$ system with large and random single--ion anisotropy can be at low energies mapped to a $S=1/2$ system with random magnetic fields. This is for example realized in \mbox{Ni(Cl$_{1-x}$Br$_{x}$)$_2$-4SC(NH$_2$)$_2$} compound (DTNX) and therefore it represents a long sought realization of random local (on-site) magnetic fields in antiferromagnetic systems. We support the mapping by numerical study of $S=1$ and effective $S=1/2$ anisotropic Heisenberg chains and find excellent agreement for static quantities and also for the spin conductivity. Such systems can therefore be used to study the effects of local random magnetic fields on transport properties.