Anomalous thermodynamics in a mixed spin-1/2 and spin-1 hexagonal nanowire system

TL;DR

This paper investigates anomalous thermodynamic behaviors, including pseudo-transitions, in a mixed spin-1/2 and spin-1 hexagonal nanowire system influenced by a crystal field, revealing sharp peaks in specific heat and induced magnetization.

Contribution

It introduces the concept of pseudo-transitions in a mixed spin nanowire system and analyzes their thermodynamic signatures using transfer matrix techniques.

Findings

Pseudo-transitions occur near the ferrimagnetic/ferromagnetic boundary.

Sharp peaks in specific heat indicate second-order-like transitions.

Induced magnetization appears under small magnetic fields at pseudo-critical temperatures.

Abstract

The mixed spin-1/2 Ising model and spin-1 Blume-Capel model in an hexagonal nanowire structure under the presence of crystal field is considered. The free energy is obtained through the transfer matrix technique, which is solved numerically. Our main result lies in the presence of pseudo-transition in low temperature region near the ferrimagnetic/ferromagnetic boundary, due to the influence of a crystal field. The evidence of a pseudo-transition is observed in several quantities. Free energy first derivative quantities like entropy and internal energy show an abrupt but continuous jump, whereas quantities associated with second derivatives of the free energy like the specific heat exhibit a strong sharp peak, quite similar to a second order phase transition. We also investigate magnetization patterns and do not find evidence of spontaneous magnetization. Nevertheless, assuming a small magnetic field, we can induce a magnetization which resembles a spontaneous magnetization at a pseudo-critical temperature.