The dependence of the spin pumping efficiency and the spin mixing conductance on the surface processing of yttrium iron garnet (YIG) before the platinum (Pt) deposition has been investigated quantitatively. The ferromagnetic resonance driven spin pumping injects a spin polarized current into the Pt layer, which is transformed into an electromotive force by the inverse spin Hall effect. Our experiments show that the spin pumping effect indeed strongly depends on the YIG/Pt interface condition. We measure an enhancement of the inverse spin Hall voltage and the spin mixing conductance by more than two orders of magnitude with improved sample preparation.

Conversion of traveling magnons into an electron carried spin current is demonstrated in a time resolved experiment using a spatially separated inductive spin-wave source and an inverse spin Hall effect (ISHE) detector. A short spin-wave packet is excited in a yttrium-iron garnet (YIG) waveguide by a microwave signal and is detected at a distance of 3 mm by an attached Pt layer as a delayed ISHE voltage pulse. The delay in the detection appears due to the finite spin-wave group velocity and proves the magnon spin transport. The experiment suggests utilization of spin waves for the information transfer over macroscopic distances in spintronic devices and circuits.

Landau-Zener (LZ) transitions of a two-level system (e. g., electronic spin in molecular magnets) coupled to one or many environmental spins (e. g., nuclear spins) are studied. For rather general interactions the LZ problem is reduced to that of a Landau-Zener grid. It is shown analytically that environmental spins initially in their ground state do not influence the staying probability P. This changes if they are prepared in a statistical ensemble. For a more specific model with environmental spins in a transverse field, LZ transitions are studied in the case of well-separated resonances in the LZ grid. The full evolution of the system is described as a succession of elemenary transitions at avoided crossings and free evolution between them. If the environmental spins are strongly coupled to the central spin, their effect on P is weak. In other cases LZ transitions are strongly suppressed and P is decreasing very slowly with the sweep-rate parameter epsilon ~ 1/v, v being the energy sweep rate.Comment: 12 PR pages, 8 figures, submitted to PR

Ion-bombardment effects in a magnetic trilayer Fe (10 nm)/Cr (0.7 nm)/Fe (10 nm) system have been studied by 3D atom probe tomography (APT). The films were bombarded by 30 keV Ga+ ions at low fluences. From APT, the positions of individual Cr and Fe atoms could be located with sub-nm spatial resolution, both before and after ion bombardment. In the pristine specimen the presence of the 0.7 nm Cr layer was verified and individual lattice planes with a spacing of ∼0.15 nm were identified which would correspond to the monolayer spacing of the Fe lattice, in agreement with the growth process. Upon irradiation, the Cr layer is broadened to ∼1.2 nm at a fluence of 3 × 1014 Ga+ cm−2 and to ∼3.4 nm at 3 × 1015 Ga+ cm−2. Computer simulations indicate that, at a fluence of 3 × 1014 Ga+ cm−2, each Cr atom in the intermediate layer is displaced on average once in the collision processes.