An empirical scaling law for acquisition of thermoremanent magnetization

We describe a universal linear relationship between the acquisition magnetic field, B, and thermoremanent magnetization M-tr(T-r) measured at room temperature T-r. The efficiency epsilon(T-r) of a remanent magnetization (REM) is the ratio of the natural remanent magnetization M-nr(T-r) to the saturation remanence J(sr)(T-r). We report a power law relationship with exponent related to J(s)(T-r) and unit slope indicating a linear relationship. Thus logepsilon(T-r) of M-tr(T-r) in equidimensional-shaped magnetic minerals of contrasting saturation magnetization J(s)(T-r) plots linearly with the logarithm of the applied magnetic field B along separate grain-size-independent straight lines with nearly unit slope and offsets related to J(s)(T-r), This empirical relationship is well suited for paleofield-intensity estimation, predicts strong magnetization of hematite and pyrrhotite in weak fields, and can be used as an assessment tool for observed remanence in planetary and meteoritic objects. (C) 2004 Elsevier B.V. All rights reserved.