Crossover from itinerant to localized magnetic excitations through the metal-insulator transition inNaOsO3

Abstract

NaOsO 3 undergoes a metal-insulator transition (MIT) at 410 K, concomitant with the onset of antiferromagnetic order. The excitation spectra have been investigated through the MIT by resonant inelastic x-ray scattering (RIXS) at the Os L 3 edge. Low resolution ( E ∼ 300 meV) measurements over a wide range of energies reveal that local electronic excitations do not change appreciably through the MIT. This is consistent with a picture in which structural distortions do not drive the MIT. In contrast, high resolution ( E ∼ 56 meV) measurements show that the well-defined, low-energy magnons in the insulating state weaken and dampen upon approaching the metallic state. Concomitantly, a broad continuum of excitations develops which is well described by the magnetic fluctuations of a nearly antiferromagnetic Fermi liquid. By revealing the continuous evolution of the magnetic quasiparticle spectrum as it changes its character from itinerant to localized, our results provide unprecedented insight into the nature of the MIT in NaOsO 3 . In particular, the presence of weak correlations in the paramagnetic phase implies a degree of departure from the ideal Slater limit.

Origin of magnetic excitation gap in double perovskite Sr2FeOsO6

“…The high resolution RIXS data were fit with a Gaussian peak shape, giving excited state energies of 0.723(3), 0.934(3), 1.34(1) and 1.52(2) eV at 6 K. This compares with 0.745(7), 0.971(7), 1.447(9) and 1.68(1)eV from Ref. [3], other related 5d containing double perovskite systems [30,31] and for NaOsO 3 [32,33].…”

Aberrant electronic and structural alterations in pressure tuned perovskite NaOsO3

“…A peak at 400 cm −1 seen in Fig. 3a could represent a singlemagnon excitation observed in the NaOsO 3 RIXS experiments 8,23 . By reducing the temperature, we show that this peak exhibits three components α, β, and γ (see Fig.…”

Magnetically induced metal-insulator transition in Pb2CaOsO6

“…The lack of distinct peaks precludes further analysis of the spectrum. The width of the peaks, which far exceeds the energy resolution, is an indication of the itinerant nature of the 5d electrons as found also in NaOsO 3 [32,33].…”

“…There are four features, labeled I-IV in the figure, which resonate at slightly different energies. Based on results from other osmates with Os in octahedral coordination [31,32], these processes can be assigned as follows: I is below 1 eV and corresponds to intra-t 2g excitations; II and III at around 4 and 7 eV correspond to t 2g → e g transitions; IV corresponds to charge-transfer excitations. Figure 7(b) shows a cut through this data for incident energy E i = 10.876 keV which clearly displays the four broad features.…”