Preparation, Structure and Electronic Properties of the Series RETi0₃, RE = La, Ce, Pr, Nd, Sm, Gd, Y, and LaᵪY₁₋ᵪ

Abstract

<p>Members of the RETi0₃ series, RE = La, Ce, Pr, Nd, Gd, Y and LaᵪY₁₋ᵪ, have been prepared and characterized. Single crystals (or crystals with a small volume of twinned component) of many of these phases have been obtained from the melt for the first time using Czochralski and Stockbarger techniques.</p> <p>Crystal structures of selected members of this series have been solved using single crystal X-ray diffraction data. The solutions were complicated in some cases by twinning, but all phases were found to be isostructural with GdFe0₃, space group Pbnm. While most aspects of the structures varied smoothly across the series, the environment of the Ti⁺³ ion becomes distorted in a tetragonal-like fashion for RE = Gd and Y.</p> <p>The electronic behaviour of the d-electron associated with Ti⁺³ has been investigated. In transport studies, metallic behaviour is observed at high temperatures for RE = La and Ce, accompanied by a transition to semiconducting behaviour at lower temperature. The other RETi0₃ show semiconducting behaviour over the temperature range investigated, the activation energies increasing with decreasing RE⁺³ radius. In the magnetic properties, all phases show critical temperatures well above 4.2 K, except for RE = Nd.</p> <p>An attempt is made to account for the observed properties of the RETi0₃ phases in terms of a model proposed by J.B. Goodenough in which the d-electron behaviour depends upon the effectiveness of relevant orbital overlaps.</p>