Enhanced spin-phonon-electronic coupling in a 5d oxide

Abstract

Enhanced coupling of material properties offers new fundamental insights and routes to multifunctional devices. In this context 5d oxides provide new paradigms of cooperative interactions that drive novel emergent behaviour. This is exemplified in osmates that host metal–insulator transitions where magnetic order appears intimately entwined. Here we consider such a material, the 5d perovskite NaOsO3, and observe a coupling between spin and phonon manifested in a frequency shift of 40 cm−1, the largest measured in any material. The anomalous modes are shown to involve solely Os–O interactions and magnetism is revealed as the driving microscopic mechanism for the phonon renormalization. The magnitude of the coupling in NaOsO3 is primarily due to a property common to all 5d materials: the large spatial extent of the ion. This allows magnetism to couple to phonons on an unprecedented scale and in general offers multiple new routes to enhanced coupled phenomena in 5d materials.

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

“…Attempts to do this quantitatively did not lead to a reliable solution, primarily due To summarize, orbital excitations from the ground state do not appear to vary significantly through the MIT. This corroborates the observation that the MIT is not driven by local structural distortion, which would manifest in significant variations in the crystal field parameters Dq, Dτ , and Dσ [21]. Because these excitations are intrinsically broad, it proved difficult to extract numerical estimates of the Hund's coupling J H , and spin-orbit coupling ζ , in the same manner as presented within Ref.…”

Ba2NiOsO6 : A Dirac-Mott insulator with ferromagnetism near 100 K

“…67 The largest reported spin-phonon-electron coupling was recently discovered in an osmium oxide, which further illustrates this potential of high-valent platinum group oxides. 68 Growing interest in novel physical properties, as exemplified by the FM semiconductivity of cubic Ba2NiOsO6, should motivate further study of platinum group oxides. Our report of cubic Ba2NiOsO6 heralds a new class of FM insulator oxides, which may be useful in developing a practical magnetic semiconductor that can be employed in spintronic and quantum magnetic devices.…”

Electromagnon dispersion probed by inelastic X-ray scattering in LiCrO2

“…Besides, large magnon–phonon coupling is expected for magnetic 5 d systems, where the extended d orbitals can support large modulation of the superexchange interaction due to ligand vibrations. For example, in NaOsO 3 an upward shift of the optical phonon energy by 5 meV was attributed to the onset of magnetic correlations37. 5 d systems are especially promising for IXS studies as the general lack of large single crystals prohibits detailed INS experiments.…”