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A STUDY OF THE LOW TEMPERATURE TRANSITION IN MAGNETITE AND THE INTERNAL FIELDS ACTING ON IRON NUCLEI IN SOME SPINEL FERRITES, USING MOSSBAUER ABSORBTION
HEBREW UNIV JERUSALEM (ISRAEL)
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A study has been made of the internal fields acting on Fe-57 nuclei in some spinel ferrites, with particular reference to the low temperature order-disorder transition in magnetite, using the techniques of Mossbauer absorbtion. For the Fe ions at both the octahedral and tetrahedral sites in nickel ferrite at 300 K, Gamma Fe2O03 at 85 K and 300 K, and magnetite at 85 K, the effective magnetic field at the Fe-57 nuclei is the same and equal to about 5.1 x 10 to the 5th power oe. In magnetite, the value of Heff in the Fe ions is about 4.5 x 10 to the 5th power oe at 85 K. Measurements on magne ite at room temperatures provide a microscopic confirmation of Verweys hypothesis that above the transition temperature of magnetite there is a fast exchange between the ferrous and ferric ions in the octahedral sites. The average value obtained for the chemical shift relative to stainless steel for the Fe ions in the various cases investigated was about .045 cmssec the value for the Fe ions in magnetite at 85 K was about 0.115 cmssec. Author
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