Thermodynamic signatures of chain segmentation in dilute quasi-one dimensional Ising systems

TL;DR

This paper investigates how defects affect the thermodynamic behavior of dilute quasi-one-dimensional Ising systems, revealing unique low-temperature signatures and chain segmentation effects through simulations, theory, and experiments.

Contribution

It introduces a mean-field model capturing low-temperature behavior and applies it to experimental data, establishing a link between simulations and real materials.

Findings

Low-temperature signatures in heat capacity due to chain segmentation

Finite ground-state entropy in frustrated chain embeddings

Good agreement between simulations, theory, and experiments on Tb-Y formate systems

Abstract

Heat-capacity measurements are a useful tool for understanding the complex phase behaviour of systems containing one-dimensional motifs. Here we study the signature within such measurements of the incorporation of defects into quasi-one-dimensional (q-1D) systems. Using Monte Carlo simulations, we show that, on dilution by non-interacting sites, q-1D Ising models display a low-temperature signature not present in conventional three-dimensional models. Frustrated embeddings of 1D chains show similar features to unfrustrated embeddings, with the additional emergence of a finite ground-state entropy in the former, which arises from chain segmentation. We introduce a mean-field formulation which captures the low-temperature behaviour of the model. This theoretical framework is applied to the interpretation of experimental heat-capacity measurements of the Tb$_{1-\rho}$Y$_{\rho}$(HCOO)$_3$ family of magnetocalorics. We find good correspondence between simulation and experiment, establishing this system as a canonical example of dilute q-1D magnets.