Estimating Earth’s past field strength from individual sources in archaeological ceramics using quantum diamond microscopy

Abstract When archaeological ceramics are fired in a kiln and cool, microscopic magnetic minerals can acquire a magnetisation aligned with Earth’s magnetic field, preserving information about its past strength. Conventional palaeomagnetic methods recover this signal from whole samples, but bulk measurements can mix reliable and unreliable recorders, while heating-based experiments may alter the minerals being measured. Here we present a non-heating protocol using quantum diamond microscope measurements of individual magnetic sources in a thin section of an archaeological ceramic. We use magnetic field maps to isolate near-surface magnetic anomalies, recover their magnetic moments, and track their behaviour during controlled laboratory experiments. Selectively recovered directions closely match whole-sample measurements from a cryogenic rock magnetometer. For well-separated, dipole-like sources that pass quality and behaviour filters, estimates of Earth’s past magnetic field strength agree with independent measurements from related samples. These results demonstrate that magnetic microscopy provides a promising route to high-precision micropalaeomagnetic analysis.