Transmission electron microscopy of nanoscale mineral magnetism

Abstract

Magnetic minerals are distributed widely in the natural environment and are also present in a wide range of biological organisms, including humans. Magnetite-ulvöspinel and hematiteilmenite solid solutions are the most common magnetic minerals in the Earth's crust. Their ability to record the past geomagnetic field depends on the crystal structure, chemical composition and geometric features of the consistent minerals. Magnetite and greigite crystals are also used as magnetic sensors in some microbes and animals, although their function is often still poorly understood. Recently, off-axis electron holography and Lorentz microscopy in the transmission electron microscope (TEM) have proven to be powerful techniques for studying geological and biological specimens, allowing both magnetic properties and crystallographic and chemical information to be imaged from the same region of a specimen. In this article, a selection of recent results that were obtained using these advanced TEM techniques is presented.