FMR Study of Co/Ti Bilayer Thin Films

. We focused on the interaction between two ferromagnetic cobalt layers through a non-magnetic titanium layer. The magnetic properties of the structure were characterized by ferromagnetic resonance technique (FMR). The data were collected as a function of non-magnetic titanium layer thickness. Co/Ti multilayer (Ti (50 {\AA})/Co(45 {\AA})/Ti(2-40 {\AA})/Co(40 {\AA})/Ti(100 {\AA}))films were grown onto naturally oxidized p-type single crystal Si (100) substrate at UHV condition with magnetron sputtering system at room temperature. The thickness of Ti spacer layer ranges from 2 to 40 {\AA} with 2 {\AA} steps. We did not observe usual optic and acoustic modes; instead we had two broad overlapped peaks for the films ranged from 6 {\AA} to 40 {\AA}. One interesting result was the high anisotropic resonance field values for these films. Exchange coupling between ferromagnetic layers causes shift on resonance field values but these shifts in our samples were much larger than expected. This large anisotropic behavior is not clear at the moment. Our theoretical model was not able to determine a value for the exchange coupling parameter. One reason can be the close thickness values for Co sublayers. The other reason can be the Ti non-magnetic layer. If titanium did not grow layer by layer on cobalt, the cobalt ferromagnetic layers may behave as a single layer. As a result one cannot observe exchange interaction between ferromagnetic layers through non-magnetic spacer.Comment: 6 pages, 5 figure

Magnetic properties of triethylene glycol coated CoFe2O4 and Mn0.2Co0.8Fe2O4 NP's synthesized by polyol method

AbstractIn this study, we reported on the structural and magnetic properties of TEG-CoFe2O4 and TEG-Mn0.2Co0.8Fe2O4 nanocomposites produced by the glycothermal reaction (polyol). X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibration sample magnetometer (VSM) analysis have been carried out in order to understand the effect of Mn2+ into CoFe2O4 and it was observed that the addition of Mn2+ tends to reduce the crystallite size, increase the ao (cell parameter) and increase the TB. The presence of adsorbed polyol entities on the surface of the CoFe2O4 and Mn0.2Co0.8Fe2O4 NP's was also proven by TG measurements. FT-IR analysis suggested the presence of adsorbed TEG molecules on the surface of CoFe2O4 and Mn0.2Co0.8Fe2O4 NP's

Examining the Dimensionality, Reliability, and Invariance of the Depression, Anxiety, and Stress Scale–21 (DASS-21) Across Eight Countries

© The Author(s) 2020. This study evaluated the dimensionality, invariance, and reliability of the Depression, Anxiety, and Stress Scale–21 (DASS-21) within and across Brazil, Canada, Hong Kong, Romania, Taiwan, Turkey, United Arab Emirates, and the United States (N = 2,580) in college student samples. We used confirmatory factor analyses to compare the fit of four different factor structures of the DASS-21: a unidimensional model, a three-correlated-factors model, a higher order model, and a bifactor model. The bifactor model, with three specific factors (depression, anxiety, and stress) and one general factor (general distress), presented the best fit within each country. We also calculated ancillary bifactor indices of model-based dimensionality of the DASS-21 and model-based reliability to further examine the validity of the composite total and subscale scores and the use of unidimensional modeling. Results suggested the DASS-21 can be used as a unidimensional scale. Finally, measurement invariance of the best fitting model was tested across countries indicating configural invariance. The traditional three-correlated-factors model presented scalar invariance across Canada, Hong Kong, Romania, Taiwan, and the United States. Overall, these analyses indicate that the DASS-21 would best be used as a general score of distress rather than three separate factors of depression, anxiety, and stress, in the countries studied

Stigma of Seeking Psychological Services: Examining College Students Across Ten Countries/Regions

© Division of Counseling Psychology of the American Psychological Association. Stigma is an important barrier to seeking psychological services worldwide. Two types of stigma exist: public stigma and self-stigma. Scholars have argued that public stigma leads to self-stigma, and then self-stigma is the primary predictor of attitudes toward seeking psychological services. However, this assertion is largely limited to U.S. samples. The goal of this research was to provide a first step in understanding the relationship between public stigma, self-stigma, and attitudes toward seeking psychological services in international contexts (N = 3,276; Australia, Brazil, Canada, Hong Kong, Portugal, Romania, Taiwan, Turkey, United Arab Emirates, and United States). Using structural equation modeling, we found that self-stigma mediated the relationship between public stigma and attitudes toward seeking services among college students in each country and region. However, differences in path strengths emphasize the need to pay attention to the role of public and self-stigma on attitudes toward seeking psychological services throughout the world

Electrochemical aptasensor for human osteopontin detection using a DNA aptamer selected by SELEX

A DNA aptamer with affinity and specificity for human osteopontin (OPN), a potential breast cancer biomarker, was selected using the SELEX process, considering its homology rate and the stability of its secondary structures. This aptamer exhibited a satisfactory affinity towards OPN, showing dissociation constants lower than 2.5 nM. It was further used to develop a simple, label-free electrochemical aptasensor against OPN. The aptasensor showed good sensitivity towards OPN in standard solutions, being the square wave voltammetry (SWV), compared to the cyclic voltammetry, the most sensitive technique with detection and quantification limits of 1.4 ± 0.4 nM and 4.2 ± 1.1 nM, respectively. It showed good reproducibility and acceptable selectivity, exhibiting low signal interferences from other proteins, as thrombin, with 2.610 times lower current signals-off than for OPN. The aptasensor also successfully detected OPN in spiked synthetic human plasma. Using SWV, detection and quantification limits (1.3 ± 0.1 and 3.9 ± 0.4 nM) within the OPN plasma levels reported for patients with breast cancer (0.44.5 nM) or with metastatic or recurrent breast cancer (0.98.4 nM) were found. Moreover, preliminary assays, using a sample of human plasma, showed that the aptasensor and the standard ELISA method quantified similar OPN levels (2.2 ± 0.7 and 1.7 ± 0.1 nM, respectively). Thus, our aptasensor coupled with SWV represents a promising alternative for the detection of relevant breast cancer biomarkers.The authors acknowledge the financial support from the Strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and from project BioTecNorte (project number NORTE-01-0145-FEDER-000004). This work was also financially supported by Project POCI-01–0145-FEDER-006984 – Associate Laboratory LSRE-LCM and by Project UID/QUI/00616/2013 – CQ-VR both funded by FEDER - Fundo Europeu de Desenvolvimento Regional through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) – and by national funds through FCT - Fundação para a Ciência e a Tecnologia, Portugal. S. Meirinho also acknowledges the research grant provided by Project UID/EQU/50020/2013.info:eu-repo/semantics/publishedVersio

Block Shear Capacity of Bolted Connections in Cold-Reduced Steel Sheets

This paper examines the mechanisms for block shear failures of bolted connections in steel plates postulated in the design equations specified in the North American, European and Australian steel structures codes. It explains that there is only one feasible mechanism for the limit state of conventional block shear failure, that which involves tensile rupture and shear yielding, irrespective of the steel material ductility. It describes the fundamental shortcomings of various code equations for determining the block shear capacity of a bolted connection. Based on the tensile rupture and shear yielding mechanism, an in-plane shear lag factor, and the active shear resistance planes identified in the present work, this paper proposes a rational equation that is demonstrated to provide more accurate results compared to all the code equations in predicting the block shear capacities of bolted connections in G450 steel sheets subjected to concentric loading. The resistance factor of 0.8 for the proposed equation is computed with respect to the LRFD approach given in the North American specification for the design of cold-formed steel structures

Investigation of Magnetic Properties of Multilayer Thin Films with Spin-Wave Resonance

A theory has been developed to simulate spin-wave resonance (SWR) modes in the multilayer systems consisting of alternate magnetic and nonmagnetic layers. An equation of motion of magnetization with Gilbert-type damping parameter for simulating SWR modes was used. It has been realized that the theory developed for the magnetic multilayer films is suitable to study the spin dynamics and extract various magnetic parameters. It has been shown that SWR modes strongly depend on an effective magnetic anisotropy constant (Keff), interlayer exchange coupling constant (A12) and effective magnetization (Meff). The nature of the effective magnetic anisotropy and interlayer exchange coupling constants has been investigated by using the developed SWR theory in detail. The separation between optic and acoustic modes strongly depends on the magnitude of the interlayer exchange coupling constant, whereas the relative position of the acoustic and optic modes depends on the sign of A12. With increasing the interlayer exchange coupling constant, the resonance field of the optic mode decreases (increases) for ferromagnetic (antiferromagnetic) coupling. When the effective magnetic anisotropy constant increases, the resonance field of the acoustic and optic modes increases for both the ferromagnetic and antiferromagnetic couplings. The increasing of the effective magnetization results in decreasing of the resonance field of SWR mode at parallel geometry, whereas that of SWR mode increases at the perpendicular geometry. The results are compatible to the other theories and experimental results. © 2017, Springer Science+Business Media, LLC, part of Springer Nature

Effect of Post-annealing on Structural and Magnetic Properties of CoTa Alloy Thin Films

CoTa alloy thin films were prepared by using magnetron sputtering technique on Si substrates at room temperature. The effect of post-annealing on structural and magnetic properties of CoTa alloy thin films has been investigated in the temperature range of 10–300 K using X-ray reflectivity (XRR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) and vibrating sample magnetometer (VSM) techniques. It has been observed that the structural and magnetic properties of the prepared films depend on post-annealing. From XRR measurements, the thicknesses of the samples were determined. SEM images indicate the formation of the clusters on the surfaces of CoTa alloy thin film with the post-annealing. The cobalt core peaks indicate the existence of metallic cobalt in the samples. EPR spectra with paramagnetic behaviour appear for both as-grown and annealed CoTa alloy thin films. EPR and VSM measurements have indicated that after the post-annealing, paramagnetic behaviour weakens, ferromagnetic behaviour enhances and effective magnetic anisotropy forms. © 2017, Springer Science+Business Media New York

Effect of composition and temperature on the magnetic properties of BaBixLaxFe(12-2x)O19 (0.0 ? x ? 0.2) hexaferrites

Bi–La-substituted M-type barium hexaferrites, BaBixLaxFe(12-2x)O19 (0.0 ? x ? 0.2), were prepared by the standard solid-state reaction method. The effect of temperature and concentration on the structural and magnetic properties of BaBixLaxFe(12-2x)O19 hexaferrite powders has been comprehensively investigated. XRD analysis confirms the formation of M-type hexagonal crystal structure with P63/mmc space group. The average crystallite size of the powders was determined using Scherrer’s formula (in the range of 66–77 nm.). Lattice parameters were found to increase with the increase in Bi–La substitution. Magnetic properties were enhanced by substitution. Magnetic hysteresis loops were analysed using a ‘Law of Approach to Saturation’ method. It was obtained the saturation magnetization value close to the bulk value. Bi–La substitution gives rise to increase of saturation magnetization, coercive field, and effective magnetic anisotropy constant for both 10 and 300 K. It is observed from FMR measurements that resonance field increases with the concentration. The broad FMR linewidth of almost 2.5 kOe indicates the existence of the particles with randomly distributed anisotropy axis. The enhanced magnetic properties make these powders a good candidate for potential applications in permanent magnets at low cost and microwave absorption devices. © 2017, Springer-Verlag GmbH Germany