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Low temperature magnetic properties of titanomagnetites |
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| Authors: | P W Readman E Schmidbauer |
| Institution: | a Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland b Institut für Allgemeine und Angewandte Geophysik, Theresienstrasse 41, 8, München 2, B.R.D. |
| Abstract: | New measurements of high field magnetisation (Is), remanence (Is), and coercive force (Hc) are presented between 4 and 300 K for x = 0.4, 0.5, 0.6 and 0.8 (Fe3?xTixO4). For x = 0.4 a pronounced minimum is found at T 100 K and for X = 0.5 and 0.6 broad minima occur around T200 K, apparently coinciding with the temperature for K10. The magnetic properties below T60 K ar complex and were found to be significantly changed by cooling in the presence of a high magnetic field. With no applied field during cooling, a distinct decrease in Is is observed for T 60 K, at which temperature there is a peak in the value of Irs. The effe cooling is to eliminate the sharp decrease in Is, reduce Hc and to increase Irs below  60 K to a value the peak value, giving essentially a square hysteresis loop. The results are interpreted in terms of a form of crystallographic phase transition coupled to the magnetisation direction, possibly by the magnetostriction. Square hysteresis loops in ferrites have been explained by the presence of Jahn-Teller ions and, in the present case, the low temperature of the observed effect may be a consequence of the weak Fe2+ Jahn-Teller ion coupled to other effects such as spin-lattice coupling.Details of this work can be found in Schmidbauer, E. and Readman, P.W., 1982. Low temperature magnetic properties of Ti-rich Fe---Ti spinels. J. Magn. Magn. Mat., 27: 114–118. A paper reporting further work on Fe2.4Ti0.6O0.4 is in preparation. |
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