The oldest magnetic record in our solar system identified using nanometric imaging and numerical modeling

Jay Shah,Adrian R Muxworthy,András Kovács,Miguel A Valdez-Grijalva,Matthew J Genge,Lesleis Nagy,Trevor P Almeida,Karl Fabian,Sara S Russell,Wyn Williams,Rafal E Dunin-Borkowski

doi:10.1038/s41467-018-03613-1

Abstract

Recordings of magnetic fields, thought to be crucial to our solar system’s rapid accretion, are potentially retained in unaltered nanometric low-Ni kamacite (~ metallic Fe) grains encased within dusty olivine crystals, found in the chondrules of unequilibrated chondrites. However, most of these kamacite grains are magnetically non-uniform, so their ability to retain four-billion-year-old magnetic recordings cannot be estimated by previous theories, which assume only uniform magnetization. Here, we demonstrate that non-uniformly magnetized nanometric kamacite grains are stable over solar system timescales and likely the primary carrier of remanence in dusty olivine. By performing in-situ temperature-dependent nanometric magnetic measurements using off-axis electron holography, we demonstrate the thermal stability of multi-vortex kamacite grains from the chondritic Bishunpur meteorite. Combined with numerical micromagnetic modeling, we determine the stability of the magnetization of these grains. Our study shows that dusty olivine kamacite grains are capable of retaining magnetic recordings from the accreting solar system.

Highlights

Recordings of magnetic fields, thought to be crucial to our solar system’s rapid accretion, are potentially retained in unaltered nanometric low-Ni kamacite (~ metallic Fe) grains encased within dusty olivine crystals, found in the chondrules of unequilibrated chondrites
Scanning transmission electron microscope (TEM) (STEM) energy dispersive X-ray spectroscopy analysis was used to establish that the kamacite grains are almost pure Fe and are encased in forsteritic olivine
The average axial ratio (AR; length/width) of the dusty olivine kamacite grains is 1.5, they are ~ 150–600 nm in size, and are typically found to have well-defined single vortex (SV) magnetization states with their vortex cores aligned out-of-plane and with little external stray magnetic fields (Fig. 1 and Supplementary Figure 1)

Summary

Introduction

Recordings of magnetic fields, thought to be crucial to our solar system’s rapid accretion, are potentially retained in unaltered nanometric low-Ni kamacite (~ metallic Fe) grains encased within dusty olivine crystals, found in the chondrules of unequilibrated chondrites. Most of these kamacite grains are magnetically non-uniform, so their ability to retain fourbillion-year-old magnetic recordings cannot be estimated by previous theories, which assume only uniform magnetization. We study chondrules from the unequilibrated ordinary chondrite Bishunpur (LL3.1) using the advanced transmission electron microscope (TEM) technique of in-situ temperaturedependent off-axis electron holography[16] (nanometric magnetic imaging) and numerical micromagnetic modeling[17] to determine whether dusty olivine can retain a record of the magnetic field from the early solar system

Methods

Results

Conclusion