We experimentally investigate the structural, magnetic, transport, and electronic properties of two d
5 iridate double perovskite materials La
2BIrO
6 (
B = Mg, Zn). Notably, despite similar crystallographic structure, the two compounds show distinctly different magnetic behaviors. The
M
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We experimentally investigate the structural, magnetic, transport, and electronic properties of two d
5 iridate double perovskite materials La
2BIrO
6 (
B = Mg, Zn). Notably, despite similar crystallographic structure, the two compounds show distinctly different magnetic behaviors. The
M = Mg compound shows an antiferromagnetic-like linear field-dependent isothermal magnetization below its transition temperature, whereas the
M = Zn counterpart displays a clear hysteresis loop followed by a noticeable coercive field, indicative of ferromagnetic components arising from a non-collinear Ir spin arrangement. The local structure studies authenticate perceptible
M/Ir antisite disorder in both systems, which complicates the magnetic exchange interaction scenario by introducing Ir-O-Ir superexchange pathways in addition to the nominal Ir-O-
B-O-Ir super-superexchange interactions expected for an ideally ordered structure. While spin–orbit coupling (SOC) plays a crucial role in establishing insulating behavior for both these compounds, the rotational and tilting distortions of the IrO
6 (and
MO
6) octahedral units further lift the ideal cubic symmetry. Finally, by measuring the Ir-
L3 edge resonant inelastic X-ray scattering (RIXS) spectra for both the compounds, giving evidence of spin–orbit-derived low-energy inter-J-state (intra
t2g) transitions (below ~1 eV), the charge transfer (O 2
p → Ir 5
d), and the crystal field (Ir
t2g →
eg) excitations, we put forward a qualitative argument for the interplay among effective SOC, non-cubic crystal field, and intersite hopping in these two compounds.
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