Optical detection of spin transport in nonmagnetic metals.

We determine the dynamic magnetization induced in nonmagnetic metal wedges composed of silver, copper, and platinum by means of Brillouin light scattering microscopy. The magnetization is transferred from a ferromagnetic Ni80Fe20 layer to the metal wedge via the spin pumping effect. The spin pumping efficiency can be controlled by adding an insulating interlayer between the magnetic and nonmagnetic layer. By comparing the experimental results to a dynamical macroscopic spin-transport model we determine the transverse relaxation time of the pumped spin current which is much smaller than the longitudinal relaxation time.

Phase sensitive Brillouin scattering measurements with a novel magneto-optic modulator.

A recently reported phase sensitive Brillouin light scattering technique is improved by use of a magnetic modulator. This modulator is based on Brillouin light scattering in a thin ferrite film. Using this magnetic modulator in time and space Brillouin light scattering measurements, we have increased phase contrast and excluded influence of optical inhomogeneities in the sample. We also demonstrate that the quality of the resulting interference patterns can be improved by data postprocessing using the simultaneously recorded information about the reference light.

Switching magnetization of a nanoscale ferromagnetic particle using nonlocal spin injection.

We have performed nonlocal spin injection into a nanoscale ferromagnetic particle configured in a lateral spin-valve structure to switch its magnetization only by spin current. The nonlocal spin injection aligns the magnetization of the particle parallel to the magnetization of the spin injector. The spin current responsible for switching is estimated from the experiment to be about 200 microA, which is reasonable compared with the values obtained for conventional pillar structures. Interestingly, the switching always occurs from antiparallel to parallel in the particle-injector magnetic configurations, where no opposite switching is observed. Possible reasons for this discrepancy are discussed.

Theory of the radiation of dipoles placed within a multilayer system.

A rigorous theory of radiation from dipoles embedded inside an arbitrary multilayer system is presented. In particular, we derive explicit expressions for the angular distribution of the electromagnetic field and the intensity radiated by the dipole into the surrounding media. Under the assumptions of mutual incoherence of the dipole radiation the calculations are extended to a layer of radiating dipoles. Special configurations corresponding to (i) a single dipole near a dielectric interface, (ii) a dipole layer surrounded by semi-infinite dielectric media, and (iii) a dipole layer placed on top of a waveguide layer are discussed in detail. This theoretical analysis has important consequences for the optimization of optical chemical sensors and biosensors that are based on fluorescence emission.