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Magnon spectra and noncollinear magnetism
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=========================================
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Tutorial 0: Spin wave stiffness
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-------------------------------
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The spin wave stiffness and the related property exchange stiffness provides the bridge between atomistic spin dynamics and micromagnetism.
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A setup for bcc Fe where the stiffness can be calculated can be seen below
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.. literalinclude:: Stiffness/inpsd.dat
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Notice that we actually have no ``ip_mode`` nor ``mode`` sections, because here we are actually not interested in running any simulation.
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The ``posfile`` and ``momfile`` are here as follows
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.. literalinclude:: Stiffness/posfile
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.. literalinclude:: Stiffness/momfile
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The exchange interaction file ``jASD2S`` can be downloaded from :download:`here <https://raw.githubusercontent.com/UppASD/UppASD/master/examples/Mappings/bccFe-variants/jASD2S>` .
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* Calculate the spin wave stiffness for the system and examine how the results depend on the choice of ``eta_max`` and ``eta_min``.
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The output from the stiffness calculations are found in the ``asd_micro.bccFe100.out`` file.
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Tutorial 0b: Spin wave scripts
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------------------------------
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Even though the calculation of magnon spectra will be practiced on in more detail enough,
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one can also use the setup above to quickly showcase the functionality of the ``preQ.py`` and ``postQ.py`` scripts.
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These scripts are available in the repository but are continiously evolving. Up-to-date scripts are provided here: :download:`preQ.py <./Stiffness/preQ.py>` and :download:`postQ.py <./Stiffness/postQ.py>`
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* Use the ``preQ.py`` script to setup a k-space path for the spin wave dispersion in bcc Fe, run the system, and plot the resulting ``ams.png`` by using ``postQ.py``.
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Optional:
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* The ``preQ.py`` script provides several k-space paths. Compare the calculated magnon DOS ``magdos.bccFe100.out`` when using either ``qpoints D`` and ``qfile ./qfile.kpath`` or ``qpoints R`` and ``qfile ./qfile.reduced``.
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Tutorial 1: Fe in bcc and fcc crystal structures
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ip_mode M
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ip_mcanneal 1
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10000 0.001 1.00e-16 0.95
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mode M
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Temp 0.001 K Temperature of the system
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hfield 0.00000 0.00000 0.00000 Static H field
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^^^^^^^^^^^^^^^^^^^^^^^^
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1. Does the spectra follow the analytical expression?
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2. Why the spectra is shift it up?
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2. Why the spectra is shift it up?
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3. Plot the spectra without the gap around the center zone.
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4. Why there are two branches, 1 acoustic and 1 optical?
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5. Plot the spectrum for Fe fcc. Why now there is just 1 branch? Is it following the analytical expression?
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.. figure:: figures/tutorial1/fig7.png
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Fig 7. Adiabatic magnon spectra of Fe FCC.
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Tutorial 2: FM Heisenberg nearest-neighbour spin chain
nc_nvect 0.0 0.0 1.0 Pitch-vector along z and the moments rotate
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in the xy-plane
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nc_nvect 0.0 0.0 1.0 Pitch-vector along z and the moments rotate
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in the xy-plane
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qm_nvec 0 0 1 Unit-vector perpendicular to spins
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qm_svec 0 1 0 Direction of the spin
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do_sc Q
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sc_nstep 700
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sc_step 85
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do_sc_local_axis B Perform SQW along local quantization axis (SA) (Y/N/B)
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do_sc_local_axis B Perform SQW along local quantization axis (SA) (Y/N/B)
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B--> B_effxSA
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sc_window_fun 2 Choice of FFT window function (1=box, 2=Hann, 3=Hamming,
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sc_window_fun 2 Choice of FFT window function (1=box, 2=Hann, 3=Hamming,
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4=Blackman-Harris)
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.. figure:: figures/tutorial6/fig4.png
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.. figure:: figures/equations/fig5.png
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Eq 5. Excitation energy for spin waves in an isotropic ferromagnet.
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Tutorial 7: Spin wave stiffness
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-------------------------------
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The spin wave stiffness and the related property exchange stiffness provides the bridge between atomistic spin dynamics and micromagnetism.
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A setup for bcc Fe where the stiffness can be calculated can be seen below
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.. literalinclude:: Stiffness/inpsd.dat
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Notice that we actually have no ``ip_mode`` nor ``mode`` sections, because here we are actually not interested in running any simulation.
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The ``posfile`` and ``momfile`` are here as follows
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.. literalinclude:: Stiffness/posfile
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.. literalinclude:: Stiffness/momfile
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The exchange interaction file ``jASD2S`` can be downloaded from :download:`here <https://raw.githubusercontent.com/UppASD/UppASD/master/examples/Mappings/bccFe-variants/jASD2S>` .
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* Calculate the spin wave stiffness for the system and examine how the results depend on the choice of ``eta_max`` and ``eta_min``.
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The output from the stiffness calculations are found in the ``asd_micro.bccFe100.out`` file.
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Tutorial 0b: Spin wave scripts
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------------------------------
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Even though the calculation of magnon spectra will be practiced on in more detail enough,
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one can also use the setup above to quickly showcase the functionality of the ``preQ.py`` and ``postQ.py`` scripts.
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These scripts are available in the repository but are continiously evolving. Up-to-date scripts are provided here: :download:`preQ.py <https://raw.githubusercontent.com/UppASD/UppASD/refs/heads/master/ASD_Tools/preQ.py>` and :download:`postQ.py <https://raw.githubusercontent.com/UppASD/UppASD/refs/heads/master/ASD_Tools/postQ.py>`
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* Use the ``preQ.py`` script to setup a k-space path for the spin wave dispersion in bcc Fe, run the system, and plot the resulting ``ams.png`` by using ``postQ.py``.
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Optional:
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* The ``preQ.py`` script provides several k-space paths. Compare the calculated magnon DOS ``magdos.bccFe100.out`` when using either ``qpoints D`` and ``qfile ./qfile.kpath`` or ``qpoints R`` and ``qfile ./qfile.reduced``.
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