Raman studies of doped magnetite above and below the Verwey transition

The nature of the Verwey transition in magnetite (Fe(3)O(4)) remains an unsolved puzzle after more than 60 years. Impurities and dopants present in magnetite can alter the Verwey transition temperature T(v) as well as other physical characteristics of magnetite. We present the results from Raman studies of Mn-, Ni-, and Al-doped magnetites with Verwey transition temperatures ranging from 115 to 123 K. Mn and Ni substitute only in the octahedral sites of magnetite's spinel structure, while Al has been shown to occupy both octahedral and tetrahedral sites. We analyze the shifts in the Raman spectra of our samples relative to stoichiometric and oxygen deficient magnetite. Substitution sites and concentration of dopants will be discussed. In particular we discuss changes in the A(1g) 668 cm(-1) and T(2g) 538 cm(-1) modes due to doping. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3067858]