Magnetization studies of zinc-substituted magnetite
Abstract
Magnetization studies are reported for zinc ferrite, Zn$\sb{x}$Fe$\sb{3-x}$O$\sb4$ in the composition range of $0\le x\le 0.034$, to determine the effect of zinc substitution on the Verwey transition. The samples use in this study were grown by the skull melter technique and subsequently annealed to control the oxygen stoichiometry. Saturation magnetization measurements at 4.2 K established that zinc substitutes preferentially on tetrahedral sites. Anisotropy parameters consistent with these measurements were determined as a function of zinc concentration, x, and temperature. Analysis of the results indicates that the character of the transition and the transition temperature, $T\sb{V}$, vary in a manner similar to non-stoichiometric magnetite, Fe$\sb{3(1-\delta)}$O$\sb4$, with a compositional correspondence of $x\leftrightarrow 3\delta$. This correlation is rationalized by considering a model with the Fe$\sbsp{\rm A}{3+}$-O-Fe$\sbsp{\rm B}{3+}$ magnetic interaction the dominant force driving the Verwey transition. The temperature variation of the anisotropy parameters above the transition temperature indicates that the magnetic interactions responsible for the Verwey transition set in at approximately 230 K. Above this temperature the anisotropy parameters are independent of zinc concentration while at $T\sb{V}< T<230$ K, the parameters for samples undergoing continuous transitions are strong functions of zinc concentration. The anisotropy parameters below the Verwey transition follow a similar pattern.
Degree
Ph.D.
Advisors
Honig, Purdue University.
Subject Area
Chemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.