We report on the nature of the interlayer magnetic interactions in NiFe/Cu/Co films. By probing the quasi-static and dynamic magnetic properties of biphase ferromagnetic films, with soft and hard ...ferromagnetic phases intermediated by a non-magnetic layer, we address aspects of the coupling between magnetic layers. Our results demonstrate the nature of the interlayer magnetic coupling in biphase films. We also disclose the asymmetric magnetoimpedance effect as a fingerprint of the nature of the magnetic interlayer interactions playing key role in the magnetization dynamics of the system. We revisit in literature data and ideas on the asymmetric magnetoimpedance and the nature of the magnetic interactions in biphase ferromagnetic systems. Then, we compare our findings with results for biphase ribbons and microwires. Our observations raise the fundamental similarities and differences in the asymmetric magnetoimpedance of these structures.
Abstract
We investigate the magnetic nanoparticles hyperthermia in a non-adiabatic and radiating process through the calorimetric method. Specifically, we propose a theoretical approach to magnetic ...hyperthermia from a thermodynamic point of view. To test the robustness of the approach, we perform hyperthermia experiments and analyse the thermal behavior of magnetite and magnesium ferrite magnetic nanoparticles dispersed in water submitted to an alternating magnetic field. From our findings, besides estimating the specific loss power value from a non-adiabatic and radiating process, thus enhancing the accuracy in the determination of this quantity, we provide physical meaning to a parameter found in literature that still remained not fully understood, the effective thermal conductance, and bring to light how it can be obtained from experiment. In addition, we show our approach brings a correction to the estimated experimental results for specific loss power and effective thermal conductance, thus demonstrating the importance of the heat loss rate due to the thermal radiation in magnetic hyperthermia.
I examine the effect of city‐level juvenile curfews on teenage birth rates using the National Center for Health Statistics birth data from 1982 to 2002. I compare differences in birth rates between ...younger and older age groups in cities with and without curfew ordinances. Before curfew adoption, the age differential in birth rates trended similarly for cities that did and did not adopt a curfew. There were significant decreases in the age differential birth rates in cities that adopted a curfew relative to cities that did not. Curfews reduced birth rates by approximately 3 births per 1000 women ages 15–17. I find a decrease in birth rates among white women. The main results are corroborated using a variety of robustness checks and specifications.
Magnetization reversal processes occurring in amorphous CoFeB thin films of thicknesses 100 nm, 200 nm and 300 nm were experimentally investigated. Analysing hysteresis loops traced with a vectorial ...VSM and the angular behaviour of coercivity, we concluded that domain wall displacement is the leading reversal mechanism for films with 200 and 300 nm. For the thinnest sample, the same is observed for external fields applied away from the hard axis, while coherent rotation becomes import close to this axis.
•Magnetization reversal in CoFeB films occurs mainly via domain wall movement.•Angular dependence of coercivity is well fitted by the Kondorsky law.•Ferromagnetic resonance experiments indicates well defined uniaxial anisotropy.
•Feasible route to the production of core/shell nanostructure with pure phases.•Synthesis of CoFe2O4@BiFeO3 core/shell nanoparticles by coprecipitation.•Structural, morphological and magnetic ...properties in CFO@BFO.•Wasp-waisted behavior and exchange bias effect disclosing the coupling between phases.•Spin disorder in CFO@BFO core/shell nanoparticles.
We synthesize CoFe2O4@BiFeO3 core/shell nanoparticles by coprecipitation and systematically investigate the structural, morphological, and magnetic properties in such nanostructured system. Through structural and morphological characterization, we demonstrate the obtainment of core/shell nanostructure with pure phases. By performing a broad experimental magnetic analysis, we evaluate the magnetic response for the precursor phases, as well as for the core/shell nanostructure. For this latter, we identify fingerprints of the wasp-waisted behavior and exchange bias effect, disclosing the exchange coupling between the phases taking place at the interface. Further, we reveal the exchange coupling between core and shell is strongly affected by a spin glass behavior arisen from the spin disorder in the CoFe2O4@BiFeO3 core/shell nanoparticles. After all, our findings allow us to place the used procedures taking into account the coprecipitation and calcination processes as a feasible route to the production of high-quality core/shell nanostructures.
The Consolidated Omnibus Reconciliation Act of 1985 (COBRA) contained provisions granting individuals the opportunity to continue employment-based insurance coverage following qualifying events which ...would otherwise cause the loss of coverage. In this paper, I examine the impact of COBRA coverage on young adult health insurance coverage following the loss of dependent status, a qualifying event. I use the 1984 to 1989 panels of the Survey of Income Program Participation in a difference-in-differences framework to provide the first estimates of COBRA's impact on young adult insurance status. I find that individuals in the affected age group were 4.5 percentage points more likely to be insured following COBRA going into effect. This increase is largely due to gains in employer sponsored insurance - particularly as a dependent - and is robust to a variety of sensitivity checks. I find considerable heterogeneity by sex; insurance gains are concentrated among young men. These findings suggest that COBRA's access to continued employer sponsored coverage after ageing out as a dependent reduced uninsurance among young adults.
•The magnetic properties of CuO/Co and CuO/Ni thin films are investigated.•The CuO/Co and CuO/Ni systems show exchange bias below 200 and 5K, respectively.•At 5K, the CuO/Co film present rather high ...interface coupling and coercivity values.•Results suggest that the bias is due to reversal on the descending loop’s branch.
The exchange-bias properties of ferromagnetic, either Co or Ni, thin films deposited onto polycrystalline multiferroic CuO are investigated. After field cooling, the CuO/Co magnetization hysteresis loops show exchange bias at temperatures lower than 200K, while the CuO/Ni system exhibits bias below about 5K only. It is suggested that the exchange bias of CuO/Co is determined mainly by the magnetization reversal that takes place on the descending branch of the loop. Rather high values of both the interface coupling energy, 0.89erg/cm2, and coercivity, 2.44kOe, of the CuO/Co film are obtained at 5K.
We investigate the longitudinal spin Seebeck effect in CoFeB/NM bilayers, with Ta, Pd and Ru as non-magnetic NM material. By means of a quantitative approach using an equivalent circuit model, we ...determine the accurate voltage due inverse spin Hall effect measured in the non-magnetic layer beyond unveiling the role of anomalous Nernst effect and thermoeletric effects provide by metallic ferromagnetic CoFeB layer. From experimental results, we estimate the spin Seebeck coefficient for the bilayers, finding values quite compatible with those for ferromagnetic insulators reported in literature. Moreover, we address the angular dependence of the voltage curves, disclosing the non-magnetic layer affects the effective magnetic anisotropy of the whole bilayer. Hence, our results suggest the effective magnetic anisotropy may be modified to improve the thermoelectric voltage response in ferromagnetic/non-magnetic metal bilayers.
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