Semiconductor-metal transition in novel Cd2Os2O7

Lifshitz metal–insulator transition induced by the all-in/all-out magnetic order in the pyrochlore oxide Cd2Os2O7

“…1, there is a clear kink in resistivity for crystal A at 227.2 K, where the temperature derivative bends over sharply. Thus, we can determine T MI = 227.2 K unequivocally, which is close to 225 K by Sleight et al 8 and 226 K by Mandrus et al 12,13 We examined several crystals from different preparation batches by resistivity and found a small sample dependence with T MI = 227-229 K, indicating little deviation in stoichiometry or an insensitivity of the T MI against certain perturbations. The magnetic susceptibility of a polycrystalline sample shown in Fig.…”

“…1 sharply rises below T MI as expected for an opening of a BCS-type gap of 875 K (shown by a broken line), but the rise is significantly suppressed at low temperatures, followed by a finite value of 4 Ω cm at 4 K; similar behavior has been reported on single crystals and polycrystalline samples by three groups. 8,12,14 In contrast, optical measurements evidence a conventional opening of a gap of a similar magnitude. 13 In order to get insight into this issue, we have carefully examined a sample dependence in resistivity on five crystals picked up from the same or different preparation batches (Fig.…”

“…The MIT of the osmium pyrochlore oxide Cd 2 Os 2 O 7 has been known for long time since Sleight and coworkers discovered a sudden rise in resistivity below ∼225 K in 1974, 8 such as shown in Fig. 1 for our crystal.…”

Structural phase transition in the superconducting pyrochlore oxide Cd2Re2O7

“…Low temperature experiments were carried out using a cryocooler down to T = 10 K. The cell constant at each temperature was refined by the Rietveld method with a program RIETAN [9], using Si powder as an internal standard [10]. Single crystal XRD experiments were performed using the 2θ-ω scan mode in a fourcircle diffractmeter with a gas flow cooler down to T = 100 K. Specific heat and electrical resistivity were measured in a Quantum Design PPMS system equipped with a 3 He refrigerator down to T = 0.4 K. Magnetic susceptibility measurements were performed at temperatures between 1.7 and 700 K in a Quantum Design MPMS system.…”

Efectos del exceso de Mg y exceso de incorporación de Nb en posición B de pirocloro en el sistema Pb-Mg-Nb-O

“…Defect pyrochlore oxides, e.g. MSbTeO 6 (M=K, Rb, Cs, Tl, Ag) and Tl(NbTe)O 6 , are of great interest because of their potential as ionic conductors (2).…”