The acquisition of thermoremanent magnetization by multidomain single-crystal titanomagnetite |
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| Authors: | P Tucker W O'Reilly |
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| Institution: | Department of Geophysics and Planetary Physics, School of Physics, The University, Newcastle upon Tyne NE1 7RU, UK |
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| Abstract: | Summary. Large, well-characterized single-crystals of titanomagnetite of approximate composition Fe2.4Ti0.6O4 were ground into spheres and orientated along specific crystallographic axes. The field dependences of the thermoremanent magnetization (TRM) and the temperature dependences of the magnetic hysteresis properties were measured and evaluated against the available theoretical models. The models, of necessity simplifications of real materials, were unable to account for many features of the experimental curves. The discrepancies were partly resolved by consideration of the mode of blocking of each individual coercivity fraction. It was deduced that the domain-walls were pinned by both dislocation lines and by inclusions or voids. A fraction of the walls were not thermally blocked. They could however be thought of as being blocked isothermally as the applied field was relaxed. The proportion of remanence blocked in by each process was found to be dependent on the strength of the inducing field through the field dependence of the blocking temperatures. A simplified model, taking these effects into account, was developed. This predicts the main features of the TRM acquisition curve and of the alternating field and thermal demagnetization spectra. |
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