Magnon: a code for simulating linear spin-wave theory band structures

Magnon is written in Python and integrated with ASE. It can simulate magnon band structures in a broad range of magnetic systems, including collinear and non-collinear materials, systems with Q-commensurate magnetic ordering, and cases where the exchange coupling includes off-diagonal Cartesian components such as the Dzyaloshinskii–Moriya interaction (DMI) and Kitaev interactions. The library includes a set of pedagogically structured tutorials and a self-explanatory API that can be straightforwardly integrated into computational workflows to simulate magnon properties with quantitative accuracy.

See the detailed documentation and tutorials at https://magnon.readthedocs.io

Install

pip install magnon

Bandstructures in under 10 lines of code

It should be extremely easy to take exchange coupling data from the literature and reproduce the magnon bandstructure. Using Magnon, the simple script below can be used to obtain the bandstructure of BCC iron in the primitive cell..

import magnon
import magnon.build

atoms, interactions = magnon.input.create_interacting_system('Iron_BCC.poscar', 'Iron_BCC_mag_moments', 'Iron_BCC_exchange', 2)

interactions = interactions.symmetrize(atoms)
primitive_atoms, primitive_interactions, _ = magnon.build.build_primitive_cell(atoms, interactions)

magnon = magnon.MagnonSpectrum(primitive_atoms,primitive_interactions,num_threads=4)

path = primitive_atoms.get_cell().bandpath(path='GNPGHN', npoints=180)

bstruct = magnon.get_band_structure(path)
bstruct.plot(emin=0, emax=0.7, filename='Iron_BCC_bands.png')

The bandstructure of BCC Iron calculated using the above example script.

Why use Magnon?

Our core development principles are:

• Easy to use - Magnon bandstructures can be computed using less than 10 lines of Python code!
• Scalable - For handling complex cells, symmetries, and couplings.
• Integrated - Interfaces with tools such as ASE to accelerate scientific workflows. The MagnonSpectrum class mirrors the structure of ASE's Phonons class.
• Adaptable - Allows conventions for working with dimensionless or dimensionful magnetic moments, different Hamiltonian conventions, many input formats.
• Open - Built for collaboration.

The code offers:

• ASE-enabled reading of many widely used structure file formats
• Ability to read complex exchange interaction data, and rigorously check symmetry requirements
• Option to easily augment non-magnetic structure files with a magnetic moment data file
• Rapid set-up routine by simultaneously reading structural, magnetic and coupling data
• Powerful InteractionList class for working efficiently with exchange coupling data at scale
• In-built symmetrisation routines for generating full exchange couplings from a minimal description
• Unit cell standardisation to convert couplings to those of the primitive cell
• Supports ferromagnetic, antiferromagnetic and non-collinear spin configurations
• Adapts to different conventions for the Heisenberg Hamiltonian prefactor
• Able to convert from exchange couplings from unit vector spin models
• Integrated MagnonSpectrum class for easy generation of reciprocal space paths and their bandstructures. Built with the same structure as the ASE Phonons class.