USE OF RENORMALIZATION-GROUP THEORY TO EXPLAIN THE LARGE VARIATION OF DOMAIN STATES OBSERVED IN TITANOMAGNETITES AND IMPLICATIONS FOR PALEOMAGNETISM

Important experiments by Halgedahl (1991) demonstrate that a material can reach dramatically different domain states on cooling when the experiment is repeated many times. Renormalization group theory is applied to show that small thermal fluctuations close to the magnetic ordering temperature produce ''predomain'' structures. These predomain structures usually vary from one experiment to the next, even when the experimental conditions do not change. On cooling, these predomain structures are primarily responsible for determining the final domain states. Transdomain processes also occur during cooling, but these processes appear to be less important. Theory is presented to show that domain observations might be very useful to discriminate between primary thermal remanent magnetization and many forms of secondary magnetizations. In particular, a grain growth chemical remanent magnetization on the average will be characterized by a narrower distribution of magnetic domains in a given size grain than that associated with a thermal remanent magnetization.