pyMagCalc

pyMagCalc (python for Magnon Calculations) calculates spin-wave excitations based on the linear spin-wave theory. The program is written in Python using SymPy. It was used to calculate spin-wave excitations in the kagome lattice antiferromagnet KFe₃(OH)₆(SO₄)₂, the non-reciprocal magnons in α-Cu₂V₂O₇, and spin-waves excitations in Zn-doped Cu₂V₂O₇.

Requirement:

• Python3
  • SymPy
  • NumPy (1.x)
  • SciPy
  • Matplotlib
  • lmfit
  • tqdm

File Description:

• magcalc.py: calculate the spin-wave dispersion and scattering intensity
• disp_---.py: calculate and plot the spin-wave dispersion
• EQmap_---.py: calculate and plot the intensity map as a function of energy and momentum
• HKmap_---.py: calculate and plot the intensity map as a function of momenta
• lmfit_---.py: fit the dispersion
• spin_model.py: contains the information about the spin model used to calculate spin-waves by magcalc.py
• data (folder): contain the neutron scattering data for KFe₃(OH)₆(SO₄)₂, α-Cu₂V₂O₇, and Zn-doped Cu₂V₂O₇

How to run the program:

In a terminal, run the following commands

$ export PYTHONPATH=<Path to magcalc.py>
$ cd <Path to Python files>
$ mkdir pckFiles

and then run, for example,

$ python3 disp_KFe3J.py

to calculate and plot spin-wave dispersion. You must first run disp_---.py to generate and store a matrix in a .pck file. The folder pckFiles contains auxiliary files used to store matrices and calculated intensity.

One has to edit spin_model.py for a different system.

Issues:

• The code uses SymPy for symbolic manipulation and can be slow for a large system. We use multiprocessing for sympy.subs. It takes about a few minutes (on MacBook Pro M1 Pro) to generate a matrix for α-Cu₂V₂O₇ with 16 spins in a magnetic unit cell.