Structure and magnetic properties of the weak ferromagnet Sr2-xLaxIrO4

Abstract

The 5d electron-based Sr2-xLaxIrO4 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 Sr2-xLaxIrO4 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 Sr2IrO4 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 K2NiF4 ( I 4/ mmm). Electrical resistivity and magnetic properties of Sr2-xLaxIrO4 are strongly dependent on the Ir3+ content. The Sr2-xLaxIrO4 magnetic behaviour in the range of 2-240 K can be ascribed to a weak ferromagnet, produced by an array of canted antiferromagnetically ordered Ir4+ magnetic moments.