In recent years, oxides incorporating Ir4+ have attracted considerable attention of the condensed matter community, as strong spin orbit coupling and intermediary electron correlations of the 5d valence orbital lead to various exotic topological and magnetic properties [1]. Ir4+, with configuration 5d5, is typically found in an octahedral ligand field, leading to a spin-orbit coupled effective jeff = 1/2 orbital state [1, 2]. Quintessential examples of such iridates are Sr2IrO4 [3] and A2Ir2O7 pyrochlores (A = Y, Pr-Lu) [4]. In the pyrochlore structure, the Ir4+ cations are placed in a geometrically frustrated tetrahedral network and interact through f-d exchange with rare-earth cations. This leads to various emergent phenomena, including, e.g., Weyl semimetal [5] and fragmented spin ice with monopole-like excitations [6]. Synthesis of new iridates is warranted to further the understanding of the Ir4+ jeff = 1/2 state.
The present work focusses on the magnetic and structural properties of newly synthesised quaternary neodymium iridate single crystals. The present compound displays a crystal structure reminiscent of the ternary pyrochlore Nd2Ir2O7 [7], with crucial differences attributed to the Pb-based synthesis method. The crystal structure found using X-ray diffraction is analysed and compared to the pyrochlore structure, with a focus on the Ir pyrochlore-type tetrahedral sublattices with octahedral O2- environments found in both crystal lattices. The full crystal structure contains two Ir sublattices, three Nd sublattices and one Pb sublattice with a high degree of disorder in the form of vacancies. Magnetic properties, including two magnetic transitions at 41 K and 8 K, demonstrate notable similarities for the two crystal variants. The magnetic structure, fundamentally tied to the tetrahedral lattice in the pyrochlore case, is examined in the non-pyrochlore samples employing neutron diffraction.