Neutron scattering study of the Tm2Ir2O7 pyrochlore iridate

Abstract

The newly synthesized Tm 2 Ir 2 O 7 iridate is investigated using neutron scattering techniques. Powder neutron diffraction patterns confirm that Tm 2 Ir 2 O 7 crystallizes in a cubic structure of pyrochlore type, consistent with the rest of the rare-earth A 2 Ir 2 O 7 series, and the crystal structure is preserved down to 0.2 K. The thermal expansion of the crystal lattice is well described by a Debye model of lattice vibrations. A weak magnetic signal consistent with the so-called all-in-all-out magnetic order (AIAO) is traced at low temperature; however, it cannot serve as unambiguous evidence of the AIAO structure in the compound. Nondispersive magnetic excitations in energy-momentum space are observed in inelastic neutron scattering spectra of Tm 2 Ir 2 O 7 . The crystal-field scheme and parameters of the thulium iridate are refined and discussed with respect to the specific heat and magnetization data. The results are supported by mean-field calculations.

Low-temperature properties of magnetically frustrated rare-earth zirconates A 2Zr2O7

“…A significant increase of T CW was revealed in the A = Tm and Yb members. Although the same trend has been observed in heavy rare-earth A 2 Ir 2 O 7 iridates [3,57,58] crystallising in pyrochlore structure, the pyrochlore A 2 Ti 2 O 7 titanates reveal a different nonmonotonic behaviour [59]. We ascribe large negative values of determined T CW , rather than to low-energy magnetic interactions affected by crystal field, to high-energy crystal field levels only.…”