Structural, transport, and magnetic properties of the nd_1-xaxtio₃ (a = ca, sr, ba) system where 0 ≤ x ≤ 1

A series of perovskite Nd_1-xA_xTiO₃ (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 NdTiO₃ results in structural phase transitions from orthorhombic (Pbnm) to cubic (Pm3m). The Nd_1-xCa_xTiO₃ 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-xA_xTiO₃ compounds (0 ≤ x ≤ ∼0.2) orders as canted antiferromagnets. The Nd_1-xA_xTiO₃ 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.