Abstract
Rock magnetic properties of archaeomagnetic samples taken from ovens are studied. Thermal demagnetization of saturation remanences and other studies reveal the presence of: (titano)magnetite, iron oxyhydroxides, and maghemite with Tb ∼ 650°C which is stable with respect to inversion. During thermal demagnetization the soft IRM component (0.06 T) is always the strongest one, indicating the importance of the (titano)magnetite contribution. A break-up in the values of coercivity Hcr' with respect to initial mass-specific magnetic susceptibility (χ) occurs at χ ∼ 1.5 × 10-6 m3/kg and separates poorer from better quality samples in the palaeointensity experiment. Separation of bad and good Thellier experiments is also observed in the relation between the coercivities and the concentration-independent parameter SIRM/χ. Thus, the poor quality of the palaeointensity experiments for some samples can probably be ascribed to the presence of weathering products and MD magnetite grains while the good quality of these experiments is related to “soft” hysteresis properties and a broad unblocking temperature spectrum.
