Superconducting and normal-state properties of the layered boride OsB2

Abstract

OsB2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB2. OsB2 is reported to become superconducting below 2.1K. We report results of the dynamic and static magnetic susceptibilities, electrical resistivity, Hall effect, heat capacity, and penetration depth measurements on arc-melted polycrystalline samples of OsB2 to characterize its superconducting and normal-state properties. These measurements confirmed that OsB2 becomes a bulk superconductor below Tc=2.1K. Our results indicate that OsB2 is a moderate-coupling type-II superconductor with an electron-phonon coupling constant λep≈0.4–0.5, a small Ginzburg-Landau parameter κ∼1–2, and an upper critical magnetic field Hc2(0.5K)∼420Oe for an unannealed sample and Hc2(1K)∼330Oe for an annealed sample. The temperature dependence of the superfluid density ns(T) for the unannealed sample is consistent with an s-wave superconductor with a slightly enhanced zero temperature gap Δ(0)=1.9kBTc and a zero temperature London penetration depth λ(0)=0.38(2)μm. The ns(T) data for the annealed sample show deviations from the predictions of the single-band s-wave BCS model. The magnetic, transport, and thermal properties in the normal state of isostructural and isoelectronic RuB2, which is reported to become superconducting below 1.6K, are also reported.

Source-reported materials — not catalogue approval

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