.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "school-tutorials/trilmax-2025/1_python-library/plot_7_lswt.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_school-tutorials_trilmax-2025_1_python-library_plot_7_lswt.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_school-tutorials_trilmax-2025_1_python-library_plot_7_lswt.py:


Linear Spin Wave theory
***********************

.. admonition:: Tutorial tasks

    * Use one of the spin Hamiltonians from the previous tutorial and compute all terms
      of the magnon Hamiltonian.
    * Compute magnon dispersion of a simple ferromagnet.
    * Compute magnon dispersion of a simple antiferromagnet.

All methods of linear spin-wave theory are grouped under the :py:class:`magnopy.LSWT`
class.

Two objects are required to create it

* Spin Hamiltonian
* Directions of spins in the ground state

.. GENERATED FROM PYTHON SOURCE LINES 20-28

.. code-block:: Python


    import numpy as np
    import magnopy

    spinham = magnopy.examples.cubic_ferro_nn(S=1, J_21=(0, 0, -0.5))

    lswt = magnopy.LSWT(spinham=spinham, spin_directions=[[0, 0, 1]])








.. GENERATED FROM PYTHON SOURCE LINES 29-33

Once created it can be used to compute terms of the magnon Hamiltonian

Correction to the classical energy
==================================

.. GENERATED FROM PYTHON SOURCE LINES 33-36

.. code-block:: Python


    print(lswt.E_2)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    -3.5




.. GENERATED FROM PYTHON SOURCE LINES 37-39

Coefficients of the one-operator terms
======================================

.. GENERATED FROM PYTHON SOURCE LINES 39-42

.. code-block:: Python


    print(lswt.O)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    [0.+0.j]




.. GENERATED FROM PYTHON SOURCE LINES 43-45

Magnon energies
===============

.. GENERATED FROM PYTHON SOURCE LINES 45-48

.. code-block:: Python


    print(lswt.omega(k=[0, 0, 0]))





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    [1.+0.j]




.. GENERATED FROM PYTHON SOURCE LINES 49-58

Parallelization
===============

Typically one wants to compute magnon energies for a set of k-points. Often for a
rather large set of k-points. Magnopy offers simple interface to parallelize the
calculations over the k-points using multiprocessing. See
:py:func:`magnopy.multiprocess_over_k` for details.
For example, to compute magnon energies for the set of k-points (that are given as
absolute coordinates in reciprocal space) utilizing two processes use

.. GENERATED FROM PYTHON SOURCE LINES 58-69

.. code-block:: Python


    kpoints = np.linspace([0, 0, 0], [1, 0, 0], 1000)

    results = magnopy.multiprocess_over_k(
        kpoints=kpoints,
        relative=False,
        function=lswt.omega,
        number_processors=2,
    )









.. GENERATED FROM PYTHON SOURCE LINES 70-71

Note that ``results[i]`` is equivalent to ``lswt.omega(k=kpoints[i], relative=False)``.

.. GENERATED FROM PYTHON SOURCE LINES 71-77

.. code-block:: Python


    print(results[42])

    print(lswt.omega(k=kpoints[42], relative=False))






.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    [1.00176727+0.j]
    [1.00176727+0.j]





.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 2.241 seconds)


.. _sphx_glr_download_school-tutorials_trilmax-2025_1_python-library_plot_7_lswt.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_7_lswt.ipynb <plot_7_lswt.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_7_lswt.py <plot_7_lswt.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_7_lswt.zip <plot_7_lswt.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_