Theory and application of the Day plot ( M rs / M s versus H cr / H c ) 1. Theoretical curves and tests using titanomagnetite data

Although most paleomagnetic and environmental magnetic papers incorporate a Day plot of the hysteresis parameters M rs / M s versus H cr / H c , a comprehensive theory covering superparamagnetic (SP), single‐domain (SD), pseudo‐single‐domain (PSD), and multidomain (MD) (titano)magnetites is lacking. There is no consensus on how to quantify grain‐size trends within the Day plot, how to distinguish MD from SP trends/mixtures, or whether magnetite, titanomagnetites, and other minerals have distinctive trends by which they might be identified. This paper develops the theory of the Day plot parameters for MD, MD + SD, PSD, and SP + SD grains of titanomagnetite (Fe 3 – x Ti x O 4 ) with compositions x = 0 (TM0 or…