Structure and magnetic properties of the weak ferromagnet Sr2−xLaxIrO4

The 5d electron-based Sr 2− x La x IrO 4 system (0≤ x ≤0.2) has been synthesized by a solid-state route. The x = 0 composition is a nonmetallic weak ferromagnet with a Curie temperature at about 240 K. The crystal structure behaviour and magnetic properties exhibited by this Sr 2− x La x IrO 4 system can be explained on the basis of the extended character of the 5d electrons of the Ir cation and its valence states. Rietveld analysis of x-ray powder diffraction on Sr 2 IrO 4 agrees well with previous structural neutron experiments. Furthermore, density functional theory (DFT) calculations predict that I 4 1 / acd represents a more stable crystal structure than K 2 NiF 4 ( I 4/ mmm ). Electrical resistivity and magnetic properties of Sr 2− x La x IrO 4 are strongly dependent on the Ir 3+ content. The Sr 2− x La x IrO 4 magnetic behaviour in the range of 2–240 K can be ascribed to a weak ferromagnet, produced by an array of canted antiferromagnetically ordered Ir 4+ magnetic moments.