Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages - supplementary data
Creators: name: Nagy, Lesleis
name: Moreno, Roberto
name: Muxworthy, Adrian R.
name: Williams, Wyn
name: Paterson, Greig A.
name: Tauxe, Lisa
name: Valdez-Grijalva, Miguel A.
Publisher: name: Zenodo
Year: 2024

description: Supplementary Materials for paper "Micromagnetic determination of the FORC response of paleomagnetically significant magnetite assemblages". The files contained herein are described as follows.

movie-s1.mp4

Domain state evolution in an equidimensional truncated octahedron (with an aspect ratio of 1.0), and a size of 130 nm (ESVD) as a function of applied field strength (from -200 mT to 200 mT) in steps of 4 mT.  Domain states in 20 identical grains are shown, each grain at different  relative  direction to the applied external field (denoted by the large grey arrows). Domain states are visualized using helicity isosurfaces, where blue indicates positive helicity and red indicates negative helicity. Averaged FORC hysteresis loops and FORC diagrams are shown on the right hand side of the video, with a red dot indicating the point on each graph that corresponds to the currently shown domain states. FORC diagram has a smoothing factor of 3.

movie-s2.mp4

Domain state evolution in an prolate truncated octahedron (with an aspect ratio of 1.5), and a size of 130 nm (ESVD) as a function of applied field strength (from -200 mT to 200 mT) in steps of 4 mT.  Domain states in 20 identical grains are shown, each grain at different  relative  direction to the applied external field (denoted by the large grey arrows). Domain states are visualized using helicity isosurfaces, where blue indicates positive helicity and red indicates negative helicity. Averaged FORC hysteresis loops and FORC diagrams are shown on the right hand side of the video, with a red dot indicating the point on each graph that corresponds to the currently shown domain states. FORC diagram has a smoothing factor of 3.

movie-s3.mp4

Domain state evolution in an oblate truncated octahedron (with an aspect ratio of 0.6667), and a size of 135 nm (ESVD) as a function of applied field strength (from -200 mT to 200 mT) in steps of 4 mT.  Domain states in 20 identical grains are shown, each grain at different  relative  direction to the applied external field (denoted by the large grey arrows). Domain states are visualized using helicity isosurfaces, where blue indicates positive helicity and red indicates negative helicity. Averaged FORC hysteresis loops and FORC diagrams are shown on the right hand side of the video, with a red dot indicating the point on each graph that corresponds to the currently shown domain states. FORC diagram has a smoothing factor of 3.

movie-s4.pdf

An atlas of simulated FORC diagrams for monodispersions of  truncated octahedral magnetites,  listed per grain size and axial ratio, with grain size as the primary index.  Scrolling though through the images shows the evolution of the FORC diagrams with grain size. We simulated the FORCs using  a maximum field of 200 mT. All models we present use a smoothing factor of 3.

movie-s5.pdf

An atlas of simulated FORC diagrams for monodispersions of  truncated octahedral magnetites,  listed per grain size and aspect ratio, with axial ratio as the primary index.  Scrolling though through the images shows the evolution of the FORC diagrams with axial ratio. We simulated the FORCs using  a maximum field of 200 mT. All models we present use a smoothing factor of 3. 

synth-forc-data.db

This is an sqlite-lite binary file containing room temperature magnetic hysteresis loops and minor loops for a set of first order reversal curves (FORC)s. The data is generated using MERRILL (https://www.rockmag.org). It can be viewed using the command line sqlite (see https://www.sqlite.org). The file contains a single table, called 'all_loops' with the following fields:

id - a unique integer id for each row in the

geometry - a unique name of a geometry in this case 'oblate' and 'prolate' indicating an oblate truncated tetrahedron and a prolate truncated tetrahedron.

temperature - the temperature at which micromagnetic models were run in order to generate the data.

aspect_ratio - the aspect ratio of the geometries.

size - the size of each geometry - in nanometre, using a convention of equivalend spherical volume diameter.

Br - the reversal field of a minor loop.

B - the applied applied field.

M - the magnetisation that results from applying B (starting from Br).

SatMag - the saturation magnetisation value of magnetite at the given temperature.

In order for the file to be consistent, it is recommended that each field step B is uniform across all geometries, sizes and aspect ratios.