A parameter characterising the irreversibility of thermomagnetic curves*1
Abstract
Previous attempts to quantify the degree of irreversibility of thermomagnetic curves have compared magnetisation during the heating and cooling cycles at a particular temperature, e.g. 100 °C. This may not give a true indication of the degree of irreversibility, as a coincidence at that temperature may occur when the thermomagnetic curve is irreversible. We suggest a new quantitative irreversibility parameter, IP, which is based on the area between the heating and cooling branches of the thermomagnetic curve. Accidental coincidences or crossovers of the branches at certain temperatures do not affect this parameter. For reversible thermomagnetic curves IP=0. In cases of strongly reduced magnetisation, e.g. due to oxidation processes during heating, IP may approach a value of -1, while for strongly increased magnetisation after heating, e.g. in the case of pyrrhotite-bearing samples, IP may exceed 1. The parameter may be also determined from high- and low-temperature variation curves of magnetic susceptibility.
- Publication:
-
Physics and Chemistry of the Earth
- Pub Date:
- 2002
- DOI:
- 10.1016/S1474-7065(02)00124-9
- Bibcode:
- 2002PCE....27.1305B