Thermodynamic curvature for a two-parameter spin model with frustration.

Area of Science:

• Statistical mechanics
• Condensed matter physics
• Thermodynamics

Background:

• Realistic thermodynamic systems often have parameters of varying macroscopic importance.
• Microscopic models require careful analysis to distinguish dominant from secondary parameters.

Purpose of the Study:

• To investigate the macroscopic relevance of two microscopic parameters, K and J, in a decorated (1+3) Ising spin chain.
• To understand how these parameters influence thermodynamic properties and magnetic phases.

Main Methods:

• Analysis of a decorated (1+3) Ising spin chain model.
• Calculation of thermodynamic observables: heat capacity C(H), magnetic susceptibility χ(T), and thermodynamic curvature R.
• Examination of parameter influence, particularly the ratio |J/K|.

Main Results:

• The stiff parameter K largely dictates macroscopic behavior.
• The sloppy parameter J has a weak effect, except near phase transitions.
• Four distinct magnetic phases (ferromagnetic, antiferromagnetic, two ferrimagnetic) were identified for large |J/K|.
• Thermodynamic curvature R, proportional to correlation length ξ, effectively characterizes these phases.

Conclusions:

• The parameter K is the primary driver of macroscopic behavior in this model.
• The thermodynamic curvature R provides a robust framework for characterizing magnetic phases.
• The findings offer insights applicable to other systems, including fluids.