Interpretation of low-temperature data part 4: The low-temperature magnetic transition of monoclinic pyrrhotite

Abstract

Use of low temperature (LT) magnetic transitions to identify magnetic minerals that carry a remanence – either natural or laboratory-induced – at room temperature, is a classic tool in rock magnetism (e.g. Nagata et al., 1964; Kosterov, 2007). This particularly applies to magnetite (Verwey transition at 118 K) and hematite (Morin transition at 265 K), transitions that are engraved in the minds of rock magnetists. A little over two decades ago, yet another LT transition has joined our toolkit: that of monoclinic pyrrhotite occurring at 32 K. This article is aimed at providing an account of the somehow complex story of this discovery (or actually its re-discovery as will become apparent), beyond what is visible in the published literature. The story will be told alternatively using first names of the three authors, or “we”, meaning Gérard and Pierre, Mark arriving on the ‘LT scene’ at a later stage