Using time- and temperature-dependent Preisach models to investigate the limitations of modelling isothermal remanent magnetization acquisition curves with cumulative log Gaussian functions
A number of recent studies have applied the cumulative log Gaussian (CLG) modelling technique to bulk isothermal remanent magnetization (IRM) curves to investigate the coercivity contributions of different minerals contained within a natural sample. Here, we present a series of Preisach-Néel models used to investigate how robust the assumption of fitting lognormal coercivity distributions is in the presence of local interaction fields and thermal relaxation. Our models indicate that the starting state of the magnetic system, magnetic interaction and thermal relaxation have a strong influence on the form of IRM curve, meaning that in a substantial number of cases the lognormal assumption fails and the CLG procedure can produce misleading interpretations. In some cases the failure of the CLG assumptions produces models which introduce spurious additional coercivity components into the fitted curve.