Frustrated magnetism and local structural disorder in pyrochlore-type Bi1.89Fe1.16Nb0.95O6.95

The magnetic properties of pyrochlore-type Bi_1.89Fe_1.16Nb_0.95O_6.95 have been investigated for the first time using AC and DC susceptibility. The compound is shown to behave as a classical spin glass due to strong competition/coexistence of ferro- and antiferromagnetic exchange. The study was accompanied by the first-ever growth of single crystals of this compound using the floating-zone method, allowing us to carry out a single-crystal neutron diffraction experiment that confirmed and extended our understanding of local structural disorder, driven by the stereochemically active 6s² electron lone pair on Bi^{3 +} ions. The magnetic properties are discussed in terms of both the topologically frustrated Fe^{3 +} lattice and the role of this local structural disorder.