Advanced Finite-Temperature Lanczos Method for anisotropic spin systems

TL;DR

This paper extends the Finite-Temperature Lanczos Method to anisotropic spin systems, enabling efficient evaluation of thermodynamic properties of large magnetic molecules without relying on symmetries.

Contribution

The authors develop an advanced FTLM that handles anisotropic effects by using symmetry-related random vectors, overcoming previous limitations due to symmetry loss.

Findings

Thermodynamic functions for large anisotropic molecules can be accurately computed.

The method effectively addresses the loss of spin rotational symmetry.

Enables analysis of magnetic molecules previously too large for exact methods.

Abstract

It is virtually impossible to evaluate the magnetic properties of large anisotropic magnetic molecules numerically exactly due to the huge Hilbert space dimensions as well as due to the absence of symmetries. Here we propose to advance the Finite-Temperature Lanczos Method (FTLM) to the case of single-ion anisotropy. The main obstacle, namely the loss of the spin rotational symmetry about the field axis, can be overcome by choosing symmetry related random vectors for the approximate evaluation of the partition function. We demonstrate that now thermodynamic functions for anisotropic magnetic molecules of unprecedented size can be evaluated.