Micromagnetic Modeling

Interpreting the paleomagnetic record of meteorites requires identifying ferromagnetic minerals that can retain a magnetic remanence, but also maintain that record over the lifetime of the solar system. One of these minerals is tetrataenite (FeNi), which is often found in meteoric metallic microstructures (see above). Tetrataenite has been used to determine the presence or absence of planetesimal dynamos on the parent bodies of the IIE, IVA, and IAB irons, main group pallasites, mesosiderites, and H chondrites.

Due to its high coercivity (>1 T), tetrataenite has de facto been thought of a stable magnetic recorder as it is unlikely to be remagnetized by an external field. However, the stability of a grain's magnetization is also connected to its domain state, which is related to how "long" the grain can retain that magnetization. In this project, we used the micromagnetic modeling software MERRILL (Micromagnetic Earth Related Robust Interpreted Language Laboratory) to determine at what grain sizes and elongations tetrataenite occupies domains states with stable magnetization (see above). We found that tetrataenite occupies the stable single domain state between ~10 and ~160 nm depending on the grain's elongation. Also, tetrataenite cannot form a single vortex state due to its high uniaxial anisotropy, instead moving directly into a two-domain state that also has a stable magnetization. This is in contrast to typically unstable multidomain states in other minerals. You can read about our findings and the implications of this project in Mansbach et al. 2022.