Structure and magnetic properties of the weak ferromagnet Sr_2−xLa_xIrO₄

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 I41/acd represents a more stable crystal structure than K2NiF4 (I4/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.

Structure, magnetism, and transport properties for Ca doping in Sr2IrO4

“…The refined results indicate that lattice constants of Sr 2 IrO 4 (x=0) are 5.518Å and 25.861Å for a and c-axis, respectively, which are consistent with previous reports. 7,17,18 Evolution of the lattice parameter a, c, c/a and Ir-O 2 -Ir bond angles (O 2 is representative of the oxygen atoms located in the IrO 2 plane.) as a function of Ca doping concentration are shown in Fig.…”

“…The four Ir-O pairs in ab-plane of IrO 6 octahedron exhibit a rotation of about 11 • around the c-axis. 7 This rotation reduces the symmetry space group to I4 1 /acd. Sr 2 IrO 4 exhibit a weak ferromagnetic insulating ground state below 240 K, in spite of the extended 5d orbital.…”

“…Sr 2 IrO 4 exhibit a weak ferromagnetic insulating ground state below 240 K, in spite of the extended 5d orbital. 7,8 This unique Mott insulating state is originate from conspiration of several interactions, including large spin-orbit coupling, strong crystal field splitting and electron correlation. 8 One significant characteristic of 5d transition metal oxides is their more extended d-orbitals than 3d and 4d compounds.…”

“…[9][10][11][12][13][14][15] Most work are about La 3+ or K + substitution for Sr 2+ . 7,[16][17][18] However, both dopants will bring carrier doping. In this paper, we choose Ca 2+ as dopants since that it has the same valence but smaller ionic radius than Sr 2+ .…”

Electronic and optical properties of La-doped Sr3Ir2O7 epitaxial thin films

“…This observation has encouraged further theoretical and experimental studies utilizing various perturbations such as chemical doping [12][13][14][15][16], pressure [17], and lattice strain [18][19][20]. The bilayer (n = 2) iridate, Sr3Ir2O7, which is in close proximity to the insulator-to-metal transition with a smaller Mott gap than Sr2IrO4 [21][22][23][24][25][26][27][28], is another intriguing material that has not been extensively studied under perturbations such as chemical doping and lattice strain.…”