Low-temperature demagnetization of saturation remanence in rocks bearing multidomain magnetite

摘要: Abstract Saturation remanence is given near room temperature to eight magnetite-bearing samples whose coercive force HC ranges from 11 152 Oe ((11–152) × 103/4π A m−1)). Intensity of JR measured while cooling the about −177°C in zero field and then reheating temperature. On at which a minimum (− 146 ± 6°C), decreases (by half on average) approximate proportion most samples, as expected multidomain grains. Because for these has been shown decrease polycrystalline saturation magnetostriction λ S during this cooling, much demagnetization probably result S, presumably unblocks domain walls pinned by internal stresses. (In contrast, change magnetocrystalline anisotropy constant K1 not major contributor only lowest does − 148°C show warming through TK = 0). further 162 5°C, there more rapid loss (averaging quarter initial remanence). This centred Verwey TV (= 4°C) restructuring forced crystallographic transition TV. back temperature, partially recovered (recovery averaging sixth Most recovery centered rather than thus