Abstract

A series of novel double perovskites La_1 + xA_1 − xInMnO_6 − δ (A = Sr, Ba) has been prepared and the room temperature crystal structures have been refined using X-ray and neutron powder diffraction. In all cases the B-site is occupied by a disordered arrangement of In³⁺ and Mn^3+/4+ cations. However, whereas La_1 + xBa_1 − xInMnO_6 − δ exhibits two octahedral tilts and exists in a body-centred cell, space group Imma, La_1 + xSr_1 − xInMnO_6 − δ adopts the three-tilt GdFeO₃ structure and has a primitive orthorhombic structure, space group Pnma. Magnetic susceptibility data show that all the compositions synthesised exhibit a spin glass freezing transition at ∼8 K. A negative magnetoresistance Δρ/ρ₀ = 10.5% was measured at 164 K in a field of 14 T.