Journal of Physics Condensed Matter · 1991 · 438 citations · 20 references
Natural SciencesMaterials SciencePhysicsCondensed Matter PhysicsPhase TransformationsSolid State PhysicsAntiferromagnetismFerromagnetismMagnetic Properties Of SolidsMagnetism In SolidsNeutron DiffractionPhase TransitionsMagnetic Ordering TransitionsMagnetic Phase DiagramMagnetic PropertiesMagnetic Sublattice StructureNeutron Diffraction Phase AnalysisOrdering PhenomenaStructural Phase TransitionsTetragonal System
An overall survey of the structural and magnetic features of the La2NiO4+ delta system is presented as a result of neutron diffraction experiments. The stoichiometric compound ( delta =0) presents two structural phase transitions. At T0 approximately=770 K, La2NiO4 transforms from tetragonal (I4/mmm) to orthorhombic (Bmab); at T1 approximately=80 K, from orthorhombic to a new tetragonal (P42/ncm) phase. Associated with this second phase transition a strong microstrain produces anisotropic broadening of Bragg reflections. La2NiO4 is three-dimensional (3D) antiferromagnetically ordered at room temperature (TN=330 K). A weak ferromagnetic component appears below T1. Oxygen excess suppress the 3D magnetic ordering and the structural phase transformations, giving rise to a non-stoichiometric compound with interstitial oxygens. A tentative phase diagram is proposed.
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Representation analysis of magnetic structures
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