Study of Similarity between Blocking Temperature Spectra of Chemical and Thermoremanent Magnetizations by Computer Simulation

Аннотация

Monte Carlo numerical simulation of the formation of chemical remanent magnetization (CRM) by the mechanism of the growth of volumes from superparamagnetic (SPM) to single-domain (SD) in the ensembles of magnetostatically interacting particles, thermoremanent magnetization (TRM), and experiments on determining paleointensity by the Thellier–Coe and Wilson–Burakov methods are carried out. The obtained results agree with the Smirnov–Tarduno hypothesis (Smirnov and Tarduno, 2005) that the similarity of the spectra of blocking temperatures T_b of CRM and TRM can be due to the narrowness of the interval of the blocking temperatures T_b of CRM and TRM, with the reservation that the similarity can be observed on part of the total interval of the T_b spectrum provided that this interval accommodates a significant fraction of the total CRM intensity. The analytical examination of the case of non-interacting particles (sparse concentration of grains) shows that in this case, the (quasi-)linearity of the Arai–Nagata diagrams is due to the presence of a plateau on the curves of the derivative dCRM/dpTRM (pTRM is partial thermoremanent magnetization) which emerges in a narrow spectrum of blocking temperatures. The results of the numerical experiments suggest that at a particle concentration of above 0.2% magnetostatic interaction leads to the practically full linearity of the Arai–Nagata diagram over a significant interval of the total spectrum of blocking temperatures for CRM. At the same time, on the remaining temperature interval, both the Arai–Nagata diagrams and the CRM(TRM) curves are substantially concave, indicating the lack of similarity between the spectra of blocking temperatures for CRM and TRM. The analysis of the empirical data revealed their resemblance, up to a certain point, to the results of simulation but at the same time clearly demonstrated the noticeable distinction between them, associated with the significant differences in the conditions of the numerical and laboratory experiments.