Comparative study of low-temperature x-ray diffraction experiments onR2Ir2O7(R=Nd

Abstract

The cubic symmetry of pyrochlore iridium oxides R 2 Ir 2 O 7 (R = Nd, Eu, and Pr) has been investigated by high resolution x-ray diffraction experiments down to 4 K, in order to clarify the relationship between the metal-insulator transition (MIT) and the small structural phase transition suggested by Raman scattering experiments in these compounds. We have found that a small negative thermal expansion of the order of 10 −3Å appears only in Nd 2 Ir 2 O 7 below the MIT, T MIT = 34 K, ascribable to the magnetovolume effect of the long-range order of Ir moments. However, any breaking of the cubic symmetry of three iridates has not been observed as appearance of superlattice reflections nor splittings of cubic reflections below T MIT . These results imply that lowering of the cubic symmetry plays a minor role for the change in the electronic state of these compounds, while a magnetic order of Ir moments plays a major role for the MIT.

Approaching the quantum critical point in a highly correlated all-in–all-out antiferromagnet

“…3b inset). This anomalous a(T) is a reflection of the overall magnetostriction, which was also observed in the antiferromagnets Nd2Ir2O7 and NiS2 at ambient pressure [25,26]. As a(T) evolves similarly to the diffraction intensity in Fig.…”

Influence of hydrostatic pressure on the bulk magnetic properties ofEu2Ir2O7

“…One important finding common to several families of these oxides is that changes in r I , the ionic radius of the rare-earth ion R 3+ , gradually tune the local crystalline environment around the transition metal ion M 4+ and the overall electronic behaviour of the compound, accordingly. This is verified for M ions belonging to the 4d (e. g., Mo) [2,3] and 5d (e. g., Ir) [4][5][6][7] groups. Here, the characteristic temperature T MI for the development of a MIT (metal-toinsulator transition) is directly controlled by the average value r I related to a gradual R 1−x R ′ x substitution [8][9][10][11].…”

Pr2Ir2O7 : When Luttinger Semimetal Meets Melko-Hertog-Gingras Spin Ice State

“…Aligned with this original motivation, many interesting phases and phenomena, including topological Mott insulator, axion insulator, Weyl semimetal, Luttinger-Abrikosov-Beneslavskii non-Fermi liquid, et al, have been proposed [11][12][13][14][15][16][17][18][19][20][21] . Despite the fruitful achievements since the original motivation [22][23][24][25][26][27][28][29] , the role of the rare-earth local moments in this system has not been extensively studied except few works 16,17,30 . Recent experiments 31,32 in Nd 2 Ir 2 O 7 and Pr 2 Ir 2 O 7 do suggest the importance of the local moments and the coupling between the local moments and the Ir conduction electrons.…”