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D. G. Hasko

Bio: D. G. Hasko is an academic researcher. The author has contributed to research in topics: Magnetoresistance & Coercivity. The author has an hindex of 5, co-authored 5 publications receiving 213 citations.

Papers
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TL;DR: In this article, the advantage of the high etch selectivity between metals in a wet etching process to develop an optimized technique for engineering magnetic materials was used for fabricating mesoscopic Ni80Fe20 dots and wires with lateral dimensions down to 0.2 μm.
Abstract: We have used the advantage of the high etch selectivity between metals in a wet etching process to develop an optimized technique for engineering magnetic materials. This method is based on electron beam lithography and optimized pattern transfer by a combination of dry and wet etching. The technique has been used in fabricating mesoscopic Ni80Fe20 dots and wires with lateral dimensions down to 0.2 μm. We have used scanning electron microscopy to verify the lateral sizes and edge acuity of the structures. The magnetic properties were characterized using magneto-optic Kerr effect and magnetoresistance measurements. A marked increase in the coercive field and the saturation field is seen as the width of the wire is decreased. The magnetoresistance change (∂R) is found to increase significantly as the width of the wire is decreased.

60 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of magnetostatic interactions on the magnetization reversal behavior of flat wire arrays using magnetoresistance (MR) measurements was investigated, and it was shown that the shape of the MR response to fields applied along the hard axis is strongly dependent on interwire separation.
Abstract: We have investigated the effect of magnetostatic interactions on the magnetization reversal behavior of ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ flat wire arrays using magnetoresistance (MR) measurements. The wires are fabricated from films of thickness 500 \AA{}. As the separation s of a wire array of fixed width w=2 \ensuremath{\mu}m is increased, a crossover from the behavior characteristic of an interacting wire array to that of a single isolated wire is identified for $s/w\ensuremath{\sim}1$. For the interacting limit, $s/wl~1$, a marked reduction in the coercive field occurs as the spacing of wires of fixed width are decreased. The shape of the MR response to fields applied along the hard axis is also found to be strongly dependent on the interwire separation. We attribute this behavior to the effect of interwire dipolar interactions. MR measurements were also made as a function of the orientation of the applied field relative to the axis of the wire, in order to investigate how the shape anisotropy affects the magnetization reversal process. In \ensuremath{\mu}m-size wires we find that ``one-jump'' switching of the magnetization can occur according to the orientation of the wires with respect to the applied field.

55 citations

Journal ArticleDOI
TL;DR: In this paper, the evolution of the magnetoresistance and magnetization behavior of Ni80Fe20 wire arrays as the width (w) is reduced from 200 to 0.3 μm is reported.
Abstract: We report the evolution of the magnetoresistance (MR) and magnetization behavior of Ni80Fe20 wire arrays as the width (w) is reduced from 200 to 0.3 μm. At around 1.5 μm width, the hysteretic behavior seen in continuous films shows the near reversible behavior characteristic of spin rotation processes. At low field (H Ms), the linear MR response to the in-plane perpendicular hard axis field suggests a bulklike transverse MR effect.

51 citations

Journal ArticleDOI
TL;DR: In this paper, the static and dynamic properties of FeNi wire arrays on GaAs(001) substrates were investigated using magneto optical Kerr effect magnetometry and Brillouin light scattering in the Voigt geometry.
Abstract: We report on systematic studies of both the static and dynamic properties of FeNi wire arrays on GaAs(001) substrates. The wires were between 0.4 and 10 μm wide and were separated by twice their width. The static magnetic properties were investigated using magneto optical Kerr effect magnetometry. The dynamical magnetic properties (spin-waves) were investigated by Brillouin light scattering in the Voigt geometry. With an external field applied along the hard shape axis, the saturation field was observed to increase and the spin-wave energies decreased with decreasing wire size. For fields applied along the (easy) axis of the wire, we observed an increase in the coercive field as the width of the wire is decreased. The frequency of the surface mode was found to increase with decreasing wire size while the first volume mode frequency was found to be wire size independent.

25 citations


Cited by
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TL;DR: The fabrication methods and physical properties of ordered magnetic nanostructures with dimensions on the submicron to nanometer scale are reviewed in this article, where various types of nanofabrication techniques are described, and their capabilities and limitations in achieving magnetic nano-structures are discussed.

842 citations

Journal ArticleDOI
TL;DR: The preBötzinger Complex is a critical site, whereas pacemaker neurons may not be essential, and the possibility that coupled oscillators are involved is considered.
Abstract: ▪ Abstract Breathing is a vital behavior that is particularly amenable to experimental investigation. We review recent progress on three problems of broad interest. (i) Where and how is respiratory rhythm generated? The preBotzinger Complex is a critical site, whereas pacemaker neurons may not be essential. The possibility that coupled oscillators are involved is considered. (ii) What are the mechanisms that underlie the plasticity necessary for adaptive changes in breathing? Serotonin-dependent long-term facilitation following intermittent hypoxia is an important example of such plasticity, and a model that can account for this adaptive behavior is discussed. (iii) Where and how are the regulated variables CO2 and pH sensed? These sensors are essential if breathing is to be appropriate for metabolism. Neurons with appropriate chemosensitivity are spread throughout the brainstem; their individual properties and collective role are just beginning to be understood.

821 citations

Journal ArticleDOI
TL;DR: In this article, a review is devoted to both the experimental and theoretical aspects of lateral converse effects observed for spin waves, with the wave vector in the 10-10 cm range, where the magnetic dipole interaction plays the most important role.

452 citations

Journal ArticleDOI
27 Aug 2009-ACS Nano
TL;DR: The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties and have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells.
Abstract: We report a general thermal transformation approach to synthesize single-crystalline magnetic transition metal oxides nanotubes/nanorings including magnetite Fe(3)O(4), maghematite gamma-Fe(2)O(3), and ferrites MFe(2)O(4) (M = Co, Mn, Ni, Cu) using hematite alpha-Fe(2)O(3) nanotubes/nanorings template. While the straightforward reduction or reduction-oxides process was employed to produce Fe(3)O(4) and gamma-Fe(2)O(3), the alpha-Fe(2)O(3)/M(OH)(2) core/shell nanostructure was used as precursor to prepare MFe(2)O(4) nanotubes via MFe(2)O(4-x) (0 < x < 1) intermediate. The transformed ferrites nanocrystals retain the hollow structure and single-crystalline nature of the original templates. However, the crystallographic orientation-relationships of cubic spinel ferrites and trigonal hematite show strong correlation with their morpologies. The hollow-structured MFe(2)O(4) nanocrystals with tunable size, shape, and composition have exhibited unique magnetic properties. Moreover, they have been demonstrated as a highly effective peroxidase mimic catalysts for laboratory immunoassays or as a universal nanocapsules hybridized with luminescent QDs for magnetic separation and optical probe of lung cancer cells, suggesting that these biocompatible magnetic nanotubes/nanorings have great potential in biomedicine and biomagnetic applications.

209 citations

Journal ArticleDOI
TL;DR: A review of spin-polarized magnetic domain walls can be found in this article, where the authors discuss a variety of different physical effects, most notably a contribution to the electrical resistance caused by the wall, and a motion of the wall driven by the spinpolarised current.
Abstract: Electrical currents flowing in ferromagnetic materials are spin-polarised as a result of the spin-dependent band structure. When the spatial direction of the polarisation changes, in a domain structure, the electrons must somehow accommodate the necessary change in direction of their spin angular momentum as they pass through the wall. Reflection, scattering, or a transfer of angular momentum onto the lattice are all possible outcomes, depending on the circumstances. This gives rise to a variety of different physical effects, most importantly a contribution to the electrical resistance caused by the wall, and a motion of the wall driven by the spin-polarised current. Historical and recent research on these topics is reviewed. Contents PAGE 1. Introduction5862. Spin-polarised current587 2.1. Tunnelling current spin polarisation589 2.2. Ballistic current spin polarisation592 2.3. Diffusive current spin polarisation5933. Magnetic Domain Walls598 3.1. Basics of domain walls598 3.1.1. Domain wall thickness and...

206 citations