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We report the discovery of superconductivity at 2.3 K in Zr5Sb3, the first superconducting member in the large compound family of the Mn5Si3-type structure. Transport, magnetic, and calorimetric measurements clearly demonstrate bulk superconductivity for Zr5Sb3 and suggest it to be a possible phonon-mediated BCS superconductor with a relatively large density of states at the Fermi level associated with the d electrons of Zr and substantially larger electron-phonon coupling compared to the Sn counterpart compound Zr5Sn3 from band structure calculations. More superconductors with even higher transition temperatures are expected to be found in this family of compounds. [ABSTRACT FROM AUTHOR]

A spin rectification effect due to the nonresonant magnetization motion has been found, which differs from the previously known spin rectification effect caused by the resonant magnetization precession at ferromagnetic resonance. A phase-resolved electrical detection technique has been used to measure the phase lag between the magnetization response and the driving microwave magnetic field, which demonstrates unambiguously the distinction between the resonant and nonresonant rectification effects. [ABSTRACT FROM AUTHOR]

The phase-resolved ferromagnetic resonance spectra has been electrically measured via a spintronic Michelson interferometer, where the nonlinear coupling between the microwave electric field and magnetic field results in time-independent fields and currents. Besides the microwave power the strength of the electrical signal strongly depends on the relative phase of microwave fields at the ferromagnetic material. Therefore, using a ferromagnetic sensor enables a quantification of microwave transmission in both the phase and amplitude, and demonstrates precision and feasibility in the determination of complex dielectric constants in both ideal dielectric materials and strongly absorbing materials. [ABSTRACT FROM AUTHOR]

The growth and geometric and electronic structures of Cr2O3 layers on the polar ZnO surfaces were characterized to determine how polar substrates can influence the properties of nonpolar films. X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy (UPS), high resolution transmission electron microscopy (HRTEM), reflection high energy electron diffraction, low energy electron diffraction, x-ray diffraction (XRD), and x-ray reflectivity (XRR) were employed to characterize the growth mode, film quality, and interfacial electronic properties. Chromium oxide growth on ZnO (0001¯) and (0001) followed the same trends: two-dimensional growth with initial disorder followed by the formation of epitaxial Cr2O3 (0001). Despite the initial disorder, HRTEM and XRD/XRR measurements on thicker films revealed an abrupt interface with the Cr2O3 lattice extending all the way to the interface. This indicates that above a critical thickness of 10-15 Cr-O3-Cr repeat units, the entire film reorganizes into an ordered structure. It is postulated that the oxygen remained ordered throughout the growth but that the chromium initially filled interstices randomly in the oxygen sublattice, which allowed the film to eventually grow with a well-defined epitaxial relationship with the substrate. The polar interfaces showed a small band offset that decayed with increasing film thickness, suggesting that the compensating charges at the interface may partially migrate to the film surface. No evidence of formal changes in the Cr oxidation state at the interfaces was seen. On the other hand, statistical analyses of UPS valence band spectra revealed an enhanced density of states near the valence band edge for Cr2O3 on ZnO (0001), consistent with stabilization of the positive interface by filling surface electronic states. In contrast, no significant valence band differences were observed between bulk Cr2O3 and thin Cr2O3 layers on ZnO (0001¯), suggesting a different charge compensation mechanism on the negative surface. The potential impact of these findings on the surface properties of chromium oxide thin films is discussed. [ABSTRACT FROM AUTHOR]

An antiferromagnetically coupled FM/NM/FM (FM = ferromagnet, NM = normal metal) trilayer structure responds to an external magnetic field by the formation of a magnetic-moment spring within the FM layers. We show that the exchange stiffness (Aex) of an FM layer can be determined by fitting the field-dependent magnetization, M(H), of the FM/NM/FM trilayer to a micromagnetic model. Using this method, we have measured the exchange stiffness of thin-film Co alloyed with Cr, Fe, Ni, Pd, Pt, and Ru. The results show that the rate at which a substituent element reduces the exchange stiffness is not directly related to its effect on the magnetization of the alloy. The observed trends have been understood by material-specific modeling based on density functional theory within the local density approximation. The stiffness measurements are in agreement with Brillouin light scattering carried out on thicker Co films. [ABSTRACT FROM AUTHOR]

The band structure and intra- and interband scattering processes of the electrons at the surface of a bismuth bilayer on Bi2Se3 have been experimentally investigated by low-temperature Fourier-transform scanning tunneling spectroscopy. The observed complex quasiparticle interference patterns are compared to a simulation based on the spin-dependent joint density of states approach using the surface-localized spectral function calculated from first principles as the only input. Thereby, the origin of the quasiparticle interferences can be traced back to intraband scattering in the bismuth-bilayer valence band and Bi2Se3 conduction band and to interband scattering between the two-dimensional topological state and the bismuth-bilayer valence band. The investigation reveals that the bilayer band gap, which is predicted to host one-dimensional topological states at the edges of the bilayer, is pushed several hundred meV above the Fermi level. This result is rationalized by an electron transfer from the bilayer to Bi2Se3 which also leads to a two-dimensional electron state in the Bi2Se3 conduction band with a strong Rashba spin splitting, coexisting with the topological state and bilayer valence band. [ABSTRACT FROM AUTHOR]

NdO0.5F0.5BiS2 is a new layered superconductor. We have studied the low-lying electronic structure of the single-crystalline NdO0.5F0.5BiS2 superconductor, whose superconducting transition temperature is 4.83 K, with angle-resolved photoemission spectroscopy. The Fermi surface consists of two small electron pockets around the X point and shows little warping along the kz direction. Our results demonstrate the multiband and two-dimensional nature of the electronic structure. The comparison between the photoemission data and the band calculations gives the renormalization factor of ∼1.14, indicating the rather weak electron correlations in this material. Moreover, we found that the actual electron doping level and Fermi surface size are much smaller than what are expected from the nominal composition, which could be largely explained by the bismuth deficiency. The small Fermi pocket size and the weak electron correlations found here put strong constraints on theory, and suggest that the BiS2-based superconductors could be conventional BCS superconductors mediated by the electron-phonon coupling. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of Bi6Fe2Ti3O18 and Bi6FeCrTi3O18 are investigated. The samples can be indexed by an orthorhombic lattice with the space group B2cb and the valence state of Fe and Cr ions is suggested to be +3 based on the x-ray photoelectron spectroscopy spectra. The sample Bi6Fe2Ti3O18 is paramagnetic with the presence of a short-range antiferromagnetic ordering; whereas Bi6FeCrTi3O18 undergoes a short-range ferrimagnetic-like transition at 106 K originating from the spin canting of the antiferromagnetic coupling of Fe-based and Cr-based sublattices via the Dzyaloshinskii-Moriya interaction due to the distorted crystal structure of Bi6Fe2Ti3O18, which are in agreement with the EPR results. The magnetic structure and EPR spectra of Bi6Fe2Ti3O18 and Bi6FeCrTi3O18 can be understood by the presence of a small amount of isolated Fe3+ ions in an octahedral ligand field with a low symmetry and the coupling between the random occupancy of Fe3+ and/or Cr3+ ions in other two octahedral sites in the layered structure of Aurivilius phase. [ABSTRACT FROM AUTHOR]