We present time-resolved magneto-optical Kerr effect measurements of picosecond laser induced precessional dynamics in out-of-plane magnetized [Co(4Å)∕Pt(8Å)]n multilayer films. A fast precession of magnetization (up to 81GHz) emerges 6ps after pumping and decays within a 100ps time scale. The uniform precessional frequency was studied for varying external magnetic bias field and number of Co∕Pt repeats n. The variation of the precession frequency with external bias field is quantitatively understood using the macrospin model of the Landau-Lifshitz-Gilbert equation of motion [Phys. Z. Sowjetunion 8, 153 (1935); Phys. Rev. 100, 1243 (1955)], yielding a large perpendicular anisotropy of up to 1.0×107ergs∕cm3 for our samples. The precession frequency increases sharply with reduced n and almost saturates below n=5, suggesting a commensurate variation of the perpendicular anisotropy. A heavy damping of the precessional motion is observed with increasing n and can be explained by enhanced spin-orbit coupling in ultrathin films and interfacial effects.
Top of the crops: The direct use of a natural three-dimensional (3D) architecture in microbial fuel cells (MFCs) is reported for the first time. Stems from the crop plant kenaf (Hibiscus cannabinus) are carbonized and used as anode material in MFCs. The current density generated by the carbon is comparable to that of other 3D anodes prepared by other methods. The renewable and low-cost characteristics of this material provide an excellent basis for large-scale application in microbial bioelectrochemcial systems.
We report measurements of picosecond dynamics of individual nickel nanomagnets as a function of magnet dimension, aspect ratio, and magnetic environment. Spatial sensitivity to nanomagnet diameters as small as 125 nm is achieved by use of cavity enhancement of the magneto-optic Kerr effect (CE-MOKE). The importance of single-particle measurements without ensemble effects for extracting the size dependence of the intrinsic nanomagnet material properties is demonstrated.
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