Magnetic frustration in the context of pseudo-dipolar ionic disorder

TL;DR

This paper introduces a novel model combining frustrated magnetic interactions and pseudo-dipolar disorder, revealing unique disordered magnetic phases akin to spin liquids, with implications for real materials and experimental spin glass systems.

Contribution

It provides an analytical ground state phase diagram for this new model and demonstrates the existence of disordered phases without spin glass transitions at finite temperature.

Findings

Identification of new disordered magnetic phases called 'spin liquids' and 'semi-spin liquids'

Demonstration that these phases lack spin glass transition at finite temperature

Mapping to a loop model reveals the magnetic structure factor as a probe of positional disorder

Abstract

We consider an alternative to the usual spin glass paradigm for disordered magnetism, consisting of the previously unstudied combination of frustrated magnetic interactions and pseudo-dipolar disorder in spin positions. We argue that this model represents a general limiting case for real systems as well as a realistic model for certain binary fluorides and oxides. Furthermore, it is of great relevance to the highly topical subjects of the Coulomb phase and `charge ice'. We derive an analytical solution for the ground state phase diagram of a model system constructed in this paradigm and identify magnetic phases that remain either disordered or partially ordered even at zero temperature. These phases are of a hitherto unobserved type, but may be broadly classified as either `spin liquids' or `semi-spin liquids' in contrast to the usual spin glass or semi-spin glass. Numerical simulations are used to show that the spin liquid phase exhibits no spin glass transition at finite temperature, despite the combination of frustration and disorder. By mapping onto a model of uncoupled loops of Ising spins, we show that the magnetic structure factor of this phase acts, in the limit $T\rightarrow0$, as a sensitive probe of the positional disorder correlations. We suggest that this result can be generalized to more complex systems, including experimental realizations of canonical spin glass models.