Structural and magnetic properties of the5d2double perovskitesSr2BReO6(

Abstract

We have performed magnetic susceptibility, heat capacity, neutron powder diffraction, and muon spin relaxation experiments to investigate the magnetic ground states of the 5d 2 double perovskites Sr2YReO6 and Sr2InReO6. We find that Sr2YReO6 is a spin glass, while Sr2InReO6 hosts a non-magnetic singlet state. By making detailed comparisons with other 5d2 double perovskites, we argue that a delicate interplay between spin-orbit coupling, non-cubic crystal fields, and exchange interactions plays a key role in the great variation of magnetic ground states observed for this family of materials.

Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates

“…Despite small monoclinic structural distortions leading to non-cubic crystal fields at the Ir 4+ sites [36,39], the classical phase diagram for the FCC Heisenberg-Kitaev-Γ model with J eff = 1/2 moments is consistent with the A-type AFM ordered states [37] observed in these compounds. Similarly, a magnetic Hamiltonian with a dominant NN AFM Kitaev interaction can explain the Weiss temperatures, the AFM ordering temperatures (T N = 12 K and 7.5 K for the Mg and Zn systems respectively [36]), and the dynamical structure factors measured with inelastic neutron scattering [38].…”

“…While significant Ir/Ti site disorder ensures that Ba 3 IrTi 2 O 9 [34,35] does not crystallize in the ideal 6H-perovskite structure required for the triangular lattice Kitaev model, the ideas presented in Ref. [8] led to detailed studies of the double perovskite iridates La 2 MgIrO 6 and La 2 ZnIrO 6 in the context of the facecentered-cubic (FCC) Kitaev model [36][37][38]. Adjacent IrO 6 octahedra share parallel edges in the ideal FCC structure and therefore significant NN Kitaev exchange is possible according to the schematic presented in Fig.…”

“…We also used scattering techniques to determine the magnetic structures of La 2 MgIrO 6 , Ba 2 CeIrO 6 , and Sr 2 CeIrO 6 . Finally, we performed an inelastic neutron scattering experiment on polycrystalline samples of Ba 2 CeIrO 6 and Sr 2 CeIrO 6 , using the same experimental configuration previously reported for La 2 MgIrO 6 and La 2 ZnIrO 6 [38], in an effort to gain insight into the evolution of the spin waves and hence the magnetic Hamiltonians of the Ce samples relative to the La analogs.…”

Kitaev magnetism and fractionalized excitations in double perovskite Sm2ZnIrO6

“…1b, marked by yellow color shadings). In a pure Kitaev material, the underlying quasi-particle excitations in the form of continuum originates from Majorana fermion scattering [31][32][33] which survive even in the presence of Heisenberg exchange as a perturbative term [13,19]. In Fig 3a,b, we have shown the temperature evolution of the underlying continuum.…”

“…Kitaev interactions as dominating exchange along with the Heisenberg interactions with A typeantiferromagnetic as their GS , with a total Hamiltonian given as Unlike in case of 2D honeycomb structure these systems does not feature direct edge sharing IrO6 octahedra though they do have varying Ir-O-O-Ir exchange paths, and these multiple exchange paths may easily support oxygen mediated electron hopping leading to significant Kitaev interactions[19][20]. The smoking gun evidence for a Kitaev kind of anisotropic coupling is hidden in the quantum spin fluctuations and may reveal itself indirectly via interacting with the photon and coupling with the underlying magnetic spectrum.…”