Investigation of ultrafast demagnetization and cubic optical nonlinearity of Ni in the polar geometry

Copyright © 2004 American Institute of PhysicsFemtosecond optical pump-probe experiments were performed upon a Ni(720 Å)/Si(100) sample in the polar geometry with the pump beam close to normal incidence. A signal due to the ultrafast demagnetization effect was observed when the pump pulse was linearly polarized. When the pump was elliptically polarized, additional peaks were observed at zero time delay, resulting from the specular inverse Faraday effect (SIFE) and the specular optical Kerr effect (SOKE). By comparing measurements made with different pump helicities, the SIFE and SOKE peaks and the demagnetization signal were found to superpose in a linear fashion. From the dependence of the peak height upon the pump polarization, values of χxxyy=(1−3i)×10−10 rad cm3 erg−1 and χxyyx=(−9+2i)×10−12 rad cm3 erg−1 were deduced for the nonvanishing components of the local cubic susceptibility tensor. For applied fields less than the saturation value, the sudden reduction of the thin film demagnetizing field leads to an imbalance of the torques acting upon the magnetization, causing it to precess

Twinning in vapour-grown, large volume Cd1-xZnxTe crystals

The onset of twinning from View the MathML source to View the MathML source in large volume Cd1−xZnx Te crystals, grown by vapour transport on View the MathML source, often referred to as (211)B, oriented GaAs seeds, has been investigated using X-ray diffraction imaging (X-ray topography). Twinning is not associated with strains at the GaAs/CdTe interface as the initial growth was always in View the MathML source orientation. Nor is twinning related to lattice strains associated with injection of Zn subsequent to initial nucleation and growth of pure CdTe as in both cases twinning occurred after growth of several mm length of Cd1−xZnxTe. While in both cases examined, there was a region of disturbed growth prior to the twinning transition, in neither crystal does this strain appear to have nucleated the twinning process. In both cases, un-twinned material remained after twinning was observed, the scale of the resulting twin boundaries being sub-micron. Simultaneous twinning across the whole sample surface was observed in one sample, whereas in the other, twinning was nucleated at different points and times in the growth

Interface stability in CoFe and CoFeB based multilayers

We report grazing incidence x-ray scattering measurements made during in situ annealing of multilayers based on CoFe and CoFeB. The layer and interface structure of Co80Fe20/Ru superlattices grown on Si/Al2O3 were found to be stable at all temperatures up to 400ºC. In contrast, Co64Fe16B20/Ru superlattices, also grown on Si/Al2O3 showed loss of Kiessig fringe visibility above 270C but no evidence of Co64Fe16B20/Ru interface roughening on recrystallization of the Co64Fe16B20. We associate the changes in Kiessig fringe amplitude with increase in interface width, partly due to increase in the topological roughness, measured from the diffuse scatter away from the Bragg peaks, at the bottom Co64Fe16B20/Al2O3 interface. © 2006 Elsevier Ltd. All rights reserved