Micromagnetic examples and validation

The examples below ship with MagTense and are the recommended starting point. The Matlab and the Python versions of each test are written to mirror each other, so the same physics is checked from both interfaces.

muMag standard problems

Problem	Matlab	Python
Standard problem 2	Standard_problem_2.m	-
Standard problem 3	Standard_problem_3.m, `Standard_problem_3_unstructured_cart.m`, `Standard_problem_3_tetra.m`	std_problem_3.py
Standard problem 4	Standard_problem_4.m	std_problem_4.py
Standard problem 6	Standard_problem_6.m	std_problem_6.py

What each of these exercises do:

Standard problem 2 - the quasi-static hysteresis loop of a rectangular bar, computed with the explicit solver and swept over the width of the bar in units of the exchange length. This is the example to copy for a hysteresis calculation.
Standard problem 3 - the flower/vortex energy crossover of a cube as a function of its size in units of the exchange length. It is run on a uniform grid, on an unstructured Cartesian mesh and on a tetrahedral mesh, so it is also the example to copy for either kind of unstructured mesh. Standard_problem_3_tetra.m is the shortest illustration of a tetrahedral problem: it meshes the cube with CreateTetraMesh, hands the mesh over with a single call to setMicroMagGridTetrahedron, and lets MagTense do the rest.
Standard problem 4 - the switching dynamics of a thin film under a reversed field, compared against the published mean solutions. It is a two-stage calculation: first an s-state is relaxed, then that state is used as the initial condition for the dynamic run.
Standard problem 6 - domain-wall pinning at a phase boundary, which is the test of the spatially varying \(A_0\), \(K_0\) and \(M_s\) and of the modified exchange stencil.

Feature tests

These live in matlab/examples/Micromagnetism/MagTense_tests and in python/examples/micromagnetism/MagTense_tests, and each of them compares against an analytical result rather than against a reference simulation.

Test	What it checks
`macrogeometry_PBC_test`	Periodic boundaries through the macrogeometry method. Two cubes are repeated along one axis and the critical spacing at which the effective anisotropy vanishes is compared with the analytical prediction. The whole setup is rotated so that the axis of periodicity becomes x, y and z in turn, which validates all three directions. Two further spacings act as controls. See Macrogeometry.
`periodic_exchange_test`	Periodic exchange coupling, on a uniform grid, on an unstructured mesh and on a grain mesh. Exchange-coupled moments across the periodic boundary must end up identical. See Periodic exchange boundaries.
`shape_correction_test`	Both the shape anisotropy (shape-dependent demagnetisation) and the magnetocrystalline anisotropy give uniaxial anisotropy energies. The shape correction field rewrites the shape anisotropy so it precisely cancels the magnetocrystalline contribution. Consequently, in a successful test the magnetization stays put. See Sample shape correction.
`temperature_test`	Thermal fluctuations against the analytical angular diffusion of non-interacting moments. See Thermal fluctuations.

Other examples

CoFe_nanopillar.m - a nanopillar on an externally generated unstructured prism mesh.
python/examples/micromagnetism/adaptive_hysteresis/adaptive_hysteresis_minimal.py - the smallest possible adaptive hysteresis run, with no plotting or post-processing. adaptive_hysteresis_demo.py in the same folder adds a comparison against a fixed-step loop.

Running the test suites

Both interfaces ship a runner that executes the examples, turns each of them into a set of pass/fail checks and prints a summary table.

In Matlab, from matlab/util:

testMagTenseFunctions

The tests to run can be restricted with the environment variables MAGTENSE_TESTS and MAGTENSE_SKIP, and the CUDA and CVODE variants are selected with MAGTENSE_TEST_CUDA and MAGTENSE_TEST_CVODE. Standard problem 6 alone accounts for most of the running time.

In Python, from python/examples/micromagnetism:

python testMagTenseFunctions.py

python testMagTenseFunctions.py --list

python testMagTenseFunctions.py --tests temperature_test,std_problem_4

python testMagTenseFunctions.py --skip std_problem_6

--include-slow adds standard problem 3, which is very slow. Each example lives in its own directory and is run from there, so the figures and timer logs it produces land beside it, and the overview figure of the suite is written next to testMagTenseFunctions.py. There are in addition pytest suites in python/examples/magnetostatics and python/examples/micromagnetism/MagTense_tests.