NSFGEO-NERC: Transforming understanding of paleomagnetic recording: Insights from experimental observations and numerical predictions

Our understanding of the way in which rocks record the geomagnetic field is based on an analytical
theory which makes the assumption that particles are uniformly magnetized (i.e., they are single domain,
SD). But, it has long been known that most rocks contain grains referred to as pseudo-single-domain
(PSD); these are too big to be uniformly magnetized, and are unsuited for analytical theory.
Recent breakthroughs in numerical modeling have opened new avenues for understanding the nature of
PSD grains. Making it possible to estimate the temporal and thermal stability of PSD particles. This
approach has gained new urgency given recent results on PSD samples which call into question their
reliability for paleointensity research. The opportunity now exists to combine experimental and numerical
approaches for a radical new understanding of paleomagnetic recording, with the potential to transform
how paleointensity research is done.

Who might benefit from this research?

This is a blue skies project where the end users are primarily within the academic community, but the project does have implications for the future development of industrial applications in the technology/hard drive sectors, in addition to the general public and schools.

How might they benefit from this research?

1. Industry
There is a large multi-national manufacturing industry concerned with the design and manufacture of high-stability and high-density magnetic data storage. Although much of the development in this area is driven by experimental innovation, there has been great interest over the last 20 years on initial magnetic materials design exploration using micromagnetic models. Much of the research being done micromagnetics in the Earth Science community has focused on non-ideal magnetic materials, temporal stability of the magnetic remanence, and the effects of thermal activation, appropriate to the range of magnetic materials in rocks and the principal methods by which they become magnetised. Whilst these developments are often not the immediate focus of current research in the industrial sector, it has often been the case that unexpected commercial innovations in data storage have benefited from the work done in the Earth Sciences. Indeed, an early example of the seminal paper by Louis Néel (1955) on 'Some theoretical aspects or rock magnetism', laid the foundation for our understanding of the stability of magnetic recordings in man-made recording materials that were being developed at that time. Our proposed research again addresses this most important question in the Earth Sciences of temporal and thermal stability of magnetic remanence. What we have already seen is that the 'non-deal' magnetic recording particles we have studied can often have higher thermal and temporal stability than the 'ideal' uniformly magnetised particles favoured in the industrial data-storage sector. There is a clear overlap, therefore, in the interest of the rock-magnetic community and commercial magnetic materials sector, in identifying magnetic particles of high stability and remanence.

The proposed project is perfectly positioned to enhance the engagement across the academic-industrial sector and across the earth and material science communities. We will aim to:

a) Bring the capabilities of the data-mining micromagnetic methodology to the wider attention of Earth and materials scientists both in academia and industry.

b) Provide a platform that will facilitate collaboration between the academic and commercial sector through free and simple access to a variety of modelling tools for simulating magnetic behaviour in bulk samples containing massive numbers of magnetic particles.

2. General public and Schools
This scientific background to this project is the need to provide evidence for some of the key
questions surrounding the evolution of the Earth and its magnetic field. This evidence not only defines the start of plate tectonics and the nucleation of the inner core, but also the emergence of the protective envelope of the geomagnetic field that provided an environment conducive to the emergence of life. These questions are all of interest to the general public.