Thermodynamic and magnetocaloric properties of geometrically frustrated Ising nanoclusters

TL;DR

This paper investigates the thermodynamic and magnetocaloric properties of geometrically frustrated Ising nanoclusters, revealing step-wise magnetization and entropy variations, finite-temperature behaviors, and enhanced magnetocaloric effects through exact enumeration and Monte Carlo comparisons.

Contribution

It provides the first detailed exact enumeration analysis of thermodynamic and magnetocaloric properties of finite geometrically frustrated Ising clusters, highlighting shape and size effects.

Findings

Magnetization and entropy exhibit step-wise changes with magnetic field.

Entropy is not always decreasing with increasing field, contrary to expectations.

Enhanced magnetocaloric effects are observed in certain finite clusters.

Abstract

Thermodynamic and magnetocaloric properties of geometrically frustrated Ising spin clusters of selected shapes and sizes are studied by exact enumeration. In the ground state the magnetization and the entropy show step-wise variations with an applied magnetic field. The number of steps, their widths and heights depend on the cluster shape and size. While the character of the magnetization plateau heights is always increasing, the entropy is not necessarily decreasing function of the field, as one would expect. For selected clusters showing some interesting ground-state properties, the calculations are extended to finite temperatures by exact enumeration of densities of states in the energy-magnetization space. In zero field the focus is laid on a peculiar behavior of some thermodynamic quantities, such as the entropy, the specific heat and the magnetic susceptibility. In finite fields various thermodynamic functions are studied in the temperature-field parameter plane and particular attention is paid to the cases showing an enhanced magnetocaloric effect. The exact results on the finite clusters are compared with the thermodynamic limit behavior obtained from Monte Carlo simulations.