1,721,023 research outputs found
Magnetic Force Microscopy and Brillouin Light Scattering study of magnetostrictive Fe0.8Ga0.2 film with stripe domains
No full textWe report on Magnetic Force Microscopy (MFM) and Brillouin Light Scattering (BLS) investigation of magnetostrictive Fe0.8 Ga0.2 film with thickness
of 72 nm, grown by molecular beam epitaxy onto ZnSe/GaAs(001) substrate.
[1] When the external magnetic field, applied in the sample plane, is reduced below about 2 kOe, we observed the formation of stripe domains aligned along the direction of the magnetic field and with a perpendicular component
of the magnetization pointing alternately up and down (with respect to the film surface). This is caused by the competition between the easy-plane dipolar interaction and the out-of-plane magnetic anisotropy, induced by magnetostriction.
MFM measurements showed that the stripes direction can be rotated applying a magnetic field of increasing intensity in a direction perpendicular to the stripes axis. For H=800 Oe the stripes rotation was completed, and when the field was removed the stripe structure was preserved.
BLS measurements were performed at remanence rotating the sample around the film normal, when the stripes are prepared along the [110] direction. We observed two perpendicular standing modes having a constant frequency,
and a Damon-Eshabach (DE) like mode which exhibits a pseudo-uniaxial anisotropy showing a frequency maximum in correspondence to the perpendicular orientation between the in-plane transferred wave-vector and the
stripes axis (Fig.1). The values of the frequency of the DE-like mode were fitted (continuous curve) by means of an analytic equation including a rotatable field (Hrot ~ 1 kOe) associated with the presence of the stripe pattern.
Moreover, from a fit of the DE-like mode versus the intensity H of the inplane applied magnetic field, we found that, in contrast with an usual uniaxial anisotropy field, the value of Hrot decreases with increasing H and vanishes
when the magnetization lies entirely in plane.
[1] M. Eddrief et al. Phys. Rev. B, 84, 161410 (2011)
Magnetic anisotropies and stripes rotation in FeGa thin films studied by magnetic force microscopy and Brillouin light scattering
No full textGalfenol alloys Fe1-xGax exhibit a strong magnetostriction, whose size is very sensitive to Ga concentration [1]. In this work, we have studied the magnetic properties of Fe1-xGax epitaxial films deposited onto ZnSe/GaAs (100) as a function of both the film thickness and the Ga concentration, by means of Brillouin Ligth Scattering (BLS) and Magnetic Force Microscopy (MFM).
Thinnest films show an in-plane magnetic anisotropy resulting from the superposition of a biaxial term, typical of the bulk Fe, and a uniaxial anisotropy with the easy axis along the [1-10] direction. We found the intensity of the in-plane anisotropy decreases on increasing both the film thickness and the Ga concentration. In particular, for a Fe0.80Ga0.20 72 nm thick we observed an in-plane isotropic behaviour.
MFM measurements have pointed out the presence of stripe domain patterns at remanence for films with Gallium concentration greater than 14% and a thickness of 72 nm. In-field MFM has been employed to perform experiments of domains rotation: after the induction of stripes by the application of a field (up to 3 kOe) along a preferred orientation of the crystal, the rotation process has been produced by the application of another field placed at 45 or 90 degrees from the first one and followed by detecting the MFM signal at different field intensities. Depending on the specific orientations considered, we have observed coherent rotation of linear stripes together with transitions from stripes to labyrinth domain patterns or saw-tooth zig-zag periodic patterns. The stripes period was on the average of 120 nm. In any case, the stripes maintained the direction of the external applied field, even after field removal. This effect is known as rotatable anisotropy and is a consequence of magnetostriction.
[1] M. Eddrief et al., Phys. Rev. B 84, 161410 (2011
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Brillouin light scattering study of magnetic anisotropy in epitaxial Fe/ZnSe(100) ultrathin films
No full textBrillouin scattering study of epitaxial InSe films grown on the Si(111) 1x1-H surface
No full textBrillouin light scattering has been used to study the elastic properties of an InSe film grown epitaxially on a hydrogen-terminated non-reconstructed Si(111) surface. Both generalized Rayleigh-Sezawa and Love acoustic modes have been revealed, and their velocity dispersions measured as functions of the ratio between the film thickness and the acoustic wavelength. This enabled us to determine the complete set of InSe film elastic constants through a non-linear best-fitting procedure
Elastic properties of GaSe films epitaxially grown on the Si(111) 1x1-H surface, studied by Brillouin scattering
No full textBrillouin light scattering has been used to study the elastic properties of GaSe films of different thicknesses epitaxially grown on a hydrogen-terminated non-reconstructed Si(111) surface. Both Rayleigh and Sezawa guided acoustic modes have been revealed, and their velocity dispersion measured as a function of the ratio between the film thickness and the acoustic wavelength. This enabled us to determine four of the five GaSe film elastic constants through a non-linear best fit procedure. The fifth elastic constant c66 was obtained from detection of shear horizontal waves in the thicker film. The results obtained show that the film constants are similar to those of the bulk material, except for the shear elastic constant c44 which is appreciably lower. The values of the elastic constants thus obtained were used to calculate the Brillouin cross-section taking into account the rippling induced by surface phonons both at the free surface and at the interface. This permitted us to achieve ..
Elastic properties of GaSe films epitaxially grown on the Si(111)1 × 1-H surface, studied by Brillouin scattering
No full textVariations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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