Sr(M,Te)₂O₆ (M = Cr, Mn, Fe, Co, Ni): A Magnetically Dilute Family of Honeycomb Tellurates

Abstract

We report the synthesis and characterization of five new honeycomb tellurates with the PbSb2O6 structure type. These materials, SrM2/3Te4/3O6 (M = Cr, Mn, Fe) and SrM1/2Te3/2O6 (M = Co, Ni), are prepared by conventional solid state synthesis. Rietveld refinements of powder X-ray and neutron diffraction data reveal that these materials crystallize in the P3̅1m space group, in which M and Te are octahedrally coordinated and randomly distributed over the honeycomb sublattice. In three of these materials (M = Cr, Mn, Fe), the transition metal takes a 3+ oxidation state, and hence, charge neutrality necessitates that the honeycomb sublattice is 66% occupied by nonmagnetic Te. In the remaining two of these materials (M = Co, Ni), the transition metal takes a 2+ oxidation state, requiring that 75% of the honeycomb lattice is occupied by nonmagnetic Te. Thus, the honeycomb sublattice is highly diluted, as only 33% or 25% of the sites are occupied by a magnetic ion. These occupation values fall well-below the percolation threshold for the honeycomb lattice, p c = 70%. Accordingly, magnetic susceptibility measurements reveal no magnetic order or spin freezing down to 1.8 K.

An intermediate phase induced by dilution in a correlated Dirac Fermi system

“…Magnetic dilution has been the subject of extensive research efforts in the context of percolation phenomena. The effect of dilution on magnetic order has received extensive attention for graphene-like materials [36,53]. In this paper, we focus on a Dirac fermion system with on-site interactions and study the effects of dilution on both the magnetic order and insulatormetal transition.…”