ELECTRICAL AND MAGNETIC-PROPERTIES OF FE3-ZALZO4 (Z-LESS-THAN-0.06)

Electrical resistivity and magnetization measurements have been carrie d out on synthetic single crystals of Fe(3-z)AL(z)O(4) in the range 0 less than or equal to z<0.06. The samples were annealed to achieve the ideal 3:4 ratio of cations to anions. As has been previously reported for nonstoichiometric magnetite and for Zn- and Ti-doped magnetite, t here is a change in the nature of the Verwey transition: with increasi ng z the transformation shifts from first to higher order and then dis appears. Saturation magnetization measurements have been used to deter mine the possible distribution of divalent and trivalent iron and of t rivalent aluminum among the tetrahedrally and octahedrally coordinated interstices. Differences in the present findings from those in Zn- an d Ti-doped magnetite are pointed out and their implications are discus sed.