Metallic ferromagnetic films with magnetic damping under 1.4 × 10-3.

Low-damping magnetic materials have been widely used in microwave and spintronic applications because of their low energy loss and high sensitivity. While the Gilbert damping constant can reach 10-4 to 10-5 in some insulating ferromagnets, metallic ferromagnets generally have larger damping due to magnon scattering by conduction electrons. Meanwhile, low-damping metallic ferromagnets are desired for charge-based spintronic devices. Here, we report the growth of Co25Fe75 epitaxial films with excellent crystalline quality evident by the clear Laue oscillations and exceptionally narrow rocking curve in the X-ray diffraction scans as well as from scanning transmission electron microscopy. Remarkably, the Co25Fe75 epitaxial films exhibit a damping constant <1.4 × 10-3, which is comparable to the values for some high-quality Y3Fe5O12 films. This record low damping for metallic ferromagnets offers new opportunities for charge-based applications such as spin-transfer-torque-induced switching and magnetic oscillations.Owing to their conductivity, low-damping metallic ferromagnets are preferred to insulating ferromagnets in charge-based spintronic devices, but are not yet well developed. Here the authors achieve low magnetic damping in CoFe epitaxial films which is comparable to conventional insulating ferromagnetic YIG films.

Strong Modulation of Spin Currents in Bilayer Graphene by Static and Fluctuating Proximity Exchange Fields.

Two-dimensional materials provide a unique platform to explore the full potential of magnetic proximity-driven phenomena, which can be further used for applications in next-generation spintronic devices. Of particular interest is to understand and control spin currents in graphene by the magnetic exchange field of a nearby ferromagnetic material in graphene-ferromagnetic-insulator (FMI) heterostructures. Here, we present the experimental study showing the strong modulation of spin currents in graphene layers by controlling the direction of the exchange field due to FMI magnetization. Owing to clean interfaces, a strong magnetic exchange coupling leads to the experimental observation of complete spin modulation at low externally applied magnetic fields in short graphene channels. Additionally, we discover that the graphene spin current can be fully dephased by randomly fluctuating exchange fields. This is manifested as an unusually strong temperature dependence of the nonlocal spin signals in graphene, which is due to spin relaxation by thermally induced transverse fluctuations of the FMI magnetization.

Picosecond Spin Seebeck Effect.

We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal/Y_{3}Fe_{5}O_{12} bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal/Y_{3}Fe_{5}O_{12} interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 10^{8} A m^{-2} K^{-1}.

Tris(3-nitro-pentane-2,4-dionato-κO,O')-cobalt(III).

The structure of the title compound, [Co(C(5)H(6)NO(4))(3)], consists of a Co(III) ion octahedrally coordinated by three bidentate 3-nitro-pentane-2,4-dionate ligands. The complex was prepared via the nitration of tris-(2,4-penta-nedionato-κ(2)O,O')cobalt(III) with a solution of copper(II) nitrate in glacial acetic acid. The central C atom and the nitro group of one 3-nitro-pentane-2,4-dionate ligand are disordered over two positions with an occupancy ratio of 0.848 (4):0.152 (4). A second nitro group is also disordered over two orientations with an occupancy ratio of 0.892 (7):0.108 (7). Two of the ligand methyl groups form C-H⋯O inter-actions with two different nitro groups to form chains running along the c axis. Additional C-H⋯O inter-actions are found between ligand methyl groups and the cobalt-bound O atoms, also resulting in the formation of chains along the c axis.