Ce. Geiss et al., MAGNETIC DOMAIN OBSERVATIONS ON MAGNETITE AND TITANOMAGHEMITE GRAINS (0.5-10 MU-M), Geophysical journal international, 124(1), 1996, pp. 75-88
By using the Bitter method, we have observed the magnetic domain struc
tures of natural titanomaghemite grains and magnetite crystals (0.5-10
mu m) that were grown in a glass ceramic matrix. The observations wer
e carried out in a range of applied magnetic fields and were correlate
d to the hysteresis properties of the bulk samples. Our observations s
how that simple, lamellar structures cannot explain the high-held hyst
eresis behaviour in either the titanomaghemite or the magnetite sample
. This high-field behaviour is probably dominated by complicated, stre
ss-influenced domain structures and rotation processes. A plot of the
number of lamellar domains observed in magnetite grains versus their g
rain size yields a single-domain to two-domain transition size of 0.25
mu m.