Structural and Magnetic Properties of the Iridium Double Perovskites Ba_2–xSr_xYIrO₆

Abstract

The crystal structures of the series of ordered double perovskites Ba(2-x)Sr(x)YIrO6 (0 ≤ x ≤ 2) were refined using a combination of high-resolution synchrotron X-ray and high-intensity neutron diffraction data. The materials displayed a sequence of structures Fm3̅m(a(0)a(0)a(0)) (x = 0.6)--> I4/m(a(0)a(0)c(-)) (x = 1.0)--> I2/m(a(-)a(-)c(0)) (x = 1.4)--> P2(1)/n(a(-)a(-)c(+)) associated with increased tilting of the corner-sharing octahedra induced by increasing amount of the smaller Sr cation present. A similar sequence of transitions was induced by heating selected samples. Magnetic susceptibility measurements between 2 and 300 K showed no evidence for long-range magnetic ordering, an observation that was supported by neutron diffraction measurements, and rather strong spin-orbit coupling results in a Jeff = 0 ground state.

Iridium double perovskite Sr2YIrO6 : A combined structural and specific heat study

“…Our results are in strong contrast with the reported ones by Cao et al [20], but in full agreement with recent reports on polycrystalline samples [23,24], pointing towards a nonmagnetic ground state with the presence of a small amount of correlated J = 1/2 impurities.…”

“…More recent works on polycrystalline samples of the series Ba 2−x Sr x YIrO 6 [23,24] did not observe any signature for long-range magnetic order in this material in their magnetic susceptibility characterization, in strong contrast with Cao et al [20]. On the contrary, these reports reinforce the notion of a nonmagnetic ground state dominated by strong SOC.…”

“…Following the discussion about the Brillouin fitting in nonetheless, are not associated with long-range magnetic ordering, but with short-range correlations only. The possibility of magnetic correlations due to impurities was already pointed out for polycrystalline Ba 2−x Sr x YIrO 6 [23] and Ba 2 YIrO 6 single crystals [35].…”

“…On the contrary, these reports reinforce the notion of a nonmagnetic ground state dominated by strong SOC. In both reports [23,24] the magnetic characteristics of the system do not change significantly across the series, and the effective magnetic moment per Ir is much less than the value expected for an S = 1 system as reported by Cao et al [20], demonstrating a strongly SOC dominated ground state.…”

Diluted paramagnetic impurities in nonmagnetic Ba2YIrO6

“…16 In contrast, studies on polycrystals of the series Ba 2−x Sr x YIrO 6 reported the absence of any long-range order and no significant change in the magnetic properties upon increasing the structural disorder from cubic Ba 2 YIrO 6 with regular IrO 6 octahedra to monoclinic Sr 2 YIrO 6 with highly distorted IrO 6 octahedra, thus demonstrating that the CF splitting in Sr 2 YIrO 6 is not enough to compete with the strong spin-orbit coupling. 19,20 A recent detailed single crystal x-ray diffraction analysis of Sr 2 YIrO 6 even questioned the formerly reported monoclinic structure 15,19,21 but reported a cubic unit cell with regular IrO 6 octahedra.…”