Structural, Transport, and Magnetic Properties of the Nd 1- xA xTiO 3 ( A = Ca, Sr, Ba) System Where 0 ≤ x ≤ 1

Abstract

A series of perovskite Nd 1- x A x TiO 3 (A = Ca, Sr, Ba) compounds has been prepared by the dc-arc melting technique in the composition range 0 ≤ x ≤ ∼1.0. The substitution of Sr and Ba in NdTiO 3 results in structural phase transitions from orthorhombic ( Pbnm) to cubic ( Pm3 m). The Nd 1- x Ca x TiO 3 series remains orthorhombic throughout the range studied. Low field magnetic susceptibility measurements and remanent magnetic moment studies suggest that the Ti sublattice in the insulating Nd 1- x A x TiO 3 compounds (0 ≤ x ≤ ∼0.2) orders as canted antiferromagnets. The Nd 1- x A x TiO 3 compounds show compositionally dependent metal-insulator transitions that coincide with the disappearance of the magnetic ordering. The correlations between the structure and transport properties are discussed in terms of the Ti-O-Ti angle and Ti-O bond distance. The perovskite tolerance factor, t, is also shown to be a useful parameter to sort insulating and metallic phases in these compounds.