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1 Introduction

This is the manual for spinner and the accompanying program respin. For a quick overview of the options of both programs see their respective man pages, using the option '-h'.

This program can be used to simulate the collective properties of interacting classical spins (magnetic dipoles) on arbitrary lattices. The simulation method is the tried and tested Metropolis Monte Carlo algorithm.

The collective properties of interacting classical spins on two and three dimensional lattices are in general difficult to solve. Monte Carlo methods provide a simple and uniform numerical approach for obtaining estimates of the magnetic groundstates, transition temperatures, critical exponents, etc. in such systems.

With 'classical' spins we mean classical vector tops, free to rotate in one, two or three dimensions. Formally, spins with quantum number $S\rightarrow \infty$ are classical spins. However, in scientific studies of the magnetic properties of materials with localised spins the simulation of the classical analog often provides a quidance as to what kind of magnetic orderings can be expected. Even in the quantum limit of $S=1/2$, the spin moment of a single electron. There are of course other reasons why a real system may never be modelled accurately with this classical monte carlo program; For example if the energy of different spin configurations lie close together. In that case the magnitude of the spins itself fluctuates. Another reason may be orbital degeneracy, which add another degree of freedom to the system and can give rise to dynamically forming and breaking of super exchange bonds.

For detailed descriptions of the metropolis Monte Carlo algorithm see the following sources:

Spinner is designed to allow accurate modelling of all possible magnetic interactions, and lattice topologies, and returns all relevant thermodynamic parameters. Using the accompanying program respin the spin-spin correlation function, the chiral- and spin-nematic correlation functions from the magnetic structure produced with spinner can be obtained. The resulting magnetic structures can be viewed with Geomview.