Measurement of Magnetization at High Temperatures and the Origin of Thermoremanent Magnetization: A Review

Abstract

Recent studies on the measurements of magnetization at high temperatures are reviewed. Use of a second gradient magnetometer is the main advance in instrumentation. Direct observation of how remanent magnetization is acquired and/ or lost by changing temperature provides strong evidence about the origin of thermoremanent magnetization. According to such observation, Neel's single domain theory seems to be correct. Neel's multi domain theory (which is originally a two domain theory, but is frequently applied to grains with many domains), however, cannot explain the behavior of magnetization at high temperatures. The behavior of magnetization in pseudo single domain (psd) grains is strongly dependent on the grain size. It seems that the heterogeneity in the magnetic grains and the screening effect are the main effects which characterize the psd moment. It should be emphasized that at high temperatures, there are still many interesting phenomena which have not been adequately described and/ or explained. Some of these interesting phenomena are shown as a guide for future studies. © 1989, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.