No abstract

Results are reported of a detailed study of static and dynamic responses in symmetric systems consisting of two ferromagnetic films separated by a nonferromagnetic spacer layer. A comparison is made with experimental results for two systems grown by sputter deposition in an UHV chamber, namely, NiFe/Cu/NiFe and Fe/Cr/Fe. First, we present model calculations where the coupling between the magnetic films through magnetic dipolar, bilinear, and biquadratic exchange interactions are fully taken into account, together with surface, in-plane uniaxial, and cubic anisotropies. An analytical expression is given that can readily be used to consistently interpret magnetoresistance, magneto-optical Kerr effect, ferromagnetic resonance, and Brillouin light scattering (BLS) data in such trilayers. Application of the results to BLS data in Ni81Fe19(d)/Cu(25 Å)Ni81Fe19(d), with d=200 and 300 Å, shows that it is essential to treat the dipolar interaction adequately in moderately thick systems. The results are also applied to interpret very interesting data in Fe(40 Å)/Cr(s)/Fe(40 Å), with 5 Å<s<35 Å, investigated by the four techniques mentioned above, at room temperature. It is shown that consistent values for all magnetic parameters can be extracted from the data with a theory that treats both static and dynamic responses on equal footing.

One of the puzzles of the recent investigations on the exchange anisotropy in ferromagnetic (FM)/antiferromagnetic (AF) bilayers is the fact that different techniques yield different values for the exchange field (HE) between the layers. We report an investigation on sputtered NiFe/NiO carried out with three different techniques, namely, magneto-optical Kerr effect magnetometry (MOKE), Brillouin light scattering (BLS), and ferromagnetic resonance (FMR). In an attempt to reconcile the measurements obtained with the various techniques, we interpret the data with a model that includes the formation of a planar domain wall in the AF layer, giving rise to a torque on the FM moment represented by an effective domain wall field (HW). We find out that while the same pair of values of HE and HW provide equally good fits to the reversible FMR and BLS measurements, different pairs are necessary to fit the irreversible magnetometry data.

No abstract

Lanthanide-doped ZnAl 2 O 4 spinel was used as a luminescent marker for gunshot residue (GSR). GSR was visually identified on shooters' hands, as well as on firearms and the firing range. After the shot, GSR was collected and analyzed by several techniques, including FTIR, Raman and emission spectroscopies and SEM-EDS. It was observed that markers provide an optically and structurally unique signature for GSR, allowing their identification by the tested techniques. SEM-EDS shows that lanthanide ions act as a chemical taggant. FTIR and Raman spectra provided a chemical signature of GSR, as well as emission spectra. Thus, it was possible to unequivocally identify GSR, even when lead-free ammunition was used.By employing different emitting centers, it was also possible to distinguish between two types of ammunition, opening a new perspective for traceability.