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Sangkook Choi - One of the best experts on this subject based on the ideXlab platform.

  • radiation of spin waves from magnetic vortex cores by their dynamic motion and annihilation processes
    Applied Physics Letters, 2005
    Co-Authors: Sangkook Choi
    Abstract:

    We report on micromagnetic simulation results of radiation of strong spin waves from the cores of magnetic vortices driven by their dynamics motion or the annihilation of a vortex-antivortex pair in a rectangular shaped magnetic thin film. Such strong spin-waves are distinguished from spin wave modes typically excited in patterned magnetic elements. The spin wave excitation with relatively low frequencies of 0–22 GHz are associated with the shape of an element, a Magnetization Configuration, and an applied magnetic field, while dominating spin waves in the higher frequencies of 22–96 GHz are driven by either the motion or annihilation of vortex cores present in the confined element. The latter case yields much higher amplitudes than the former does. It is found that large torques applied at the local area of the vortex cores, driven by the large exchange fields in the core region during their dynamic motion and collapse, induce a rapid energy dissipation into the surrounding areas through the spin-wave ex...

B C Choi - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation Study of Magnetization Precession Dynamics in Submicrometer Elliptical Ni$_80$Fe$_20$Thin-Film Elements
    IEEE Transactions on Magnetics, 2006
    Co-Authors: B C Choi, Y K Hong, J. Jabal, Q.f. Xiao, K.j. Hass, G.w. Donohoe
    Abstract:

    Nonequilibrium Magnetization Configuration and magnetic switching behavior are studied using micromagnetic modeling. In particular, it is found that coherent rotation and Magnetization ringing in submicrometer Ni80Fe20 elements can be controlled by adjusting the axis-ratio of the ellipse, the thickness, and the angle of the magnetic field pulse with respect to the axis of elliptical elements. For the element with 400-nm-long axis, 200-nm-short axis, and 4.7-nm thickness, the nonuniform distribution of Magnetization results from a strong in-plane, nonuniform deMagnetization field during Magnetization precession. The simulation results indicate that uniformity in the distribution of the Magnetization during reversal is improved by reducing the length of the short axis from 200 nm to 112 nm, and reducing the thickness of the thin film from 4.7 to 3.2 nm. The modification in the geometric Configuration of the element is found to effectively suppress the Magnetization ringing

  • Micromagnetic domain structures and Magnetization switching mechanism in submicron thin film elements
    2005 IEEE International Magnetics Conference (INTERMAG), 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Experimental and numerical micromagnetic studies of the Magnetization Configuration and switching process in Pac-man (PM) shaped Ni/sub 80/Fe/sub 20/ samples with different geometries defined by the variation of the slot angle were presented. Scanning electron microscope images of patterned PM-I and PM-II magnetic elements were shown. These permalloy films were sputter deposited and their magnetic Configurations were measured. The results concluded that vortex core formation and vortex-driven complex Magnetization reversal can be effectively suppressed by modifying the slot angles. The hysteresis loops and domain Configurations during the reversal implied that PM-II elements with large slot angles were more suitable for magnetic random access memory (MRAM) applications.

  • Micromagnetic domain structures and Magnetization switching mechanism in submicrometer thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching behavior in two types, P-I and P-II, of submicrometer Pac-man-shaped Ni/sub 80/Fe/sub 20/ magnetic elements are studied using both magnetic force microscopy (MFM) and numerical simulation. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation-driven switching is replaced by quasi-coherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic Configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms.

  • Magnetization switching dynamics depending on as-patterned Magnetization state in magnetic thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, J. Ho, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching dynamics of submicrometer "Pac-man"-shaped Ni/sub 80/Fe/sub 20/ elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy (MFM), magnetooptic Kerr effect (MOKE), and micromagnetic simulations. It was found that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct Magnetization Configurations and magnetic switching mechanisms (in low frequencies), even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal. Fast Magnetization reversal is, however, found to be slightly dependent on as-patterned domain Configurations. For all elements investigated, the fast reversal leads to very complex nonequilibrium domain Configurations.

  • Magnetization Configuration and switching behavior of submicron nife elements pac man shape
    Applied Physics Letters, 2003
    Co-Authors: M H Park, Y K Hong, D W Erickson, B C Choi
    Abstract:

    Two types of submicron permalloy element, namely Pac-man, were investigated by a magnetic force microscope for Magnetization Configuration and switching behaviors. Two distinct domain Configurations, bidomain for Pac-man type I and single domain for Pac-man type II, were observed in arrays of Pac-man elements. The domain Configuration depends on the slot angle for the Pac-man type I, but is independent of the slot angle for the Pac-man type II. Array of Pac-man elements with a slot angle of 180° shows the highest switching field and the narrowest switching field distribution, as compared to rectangular and hexagonal elements of the same overall dimensions.

M H Park - One of the best experts on this subject based on the ideXlab platform.

  • Micromagnetic domain structures and Magnetization switching mechanism in submicron thin film elements
    2005 IEEE International Magnetics Conference (INTERMAG), 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Experimental and numerical micromagnetic studies of the Magnetization Configuration and switching process in Pac-man (PM) shaped Ni/sub 80/Fe/sub 20/ samples with different geometries defined by the variation of the slot angle were presented. Scanning electron microscope images of patterned PM-I and PM-II magnetic elements were shown. These permalloy films were sputter deposited and their magnetic Configurations were measured. The results concluded that vortex core formation and vortex-driven complex Magnetization reversal can be effectively suppressed by modifying the slot angles. The hysteresis loops and domain Configurations during the reversal implied that PM-II elements with large slot angles were more suitable for magnetic random access memory (MRAM) applications.

  • Micromagnetic domain structures and Magnetization switching mechanism in submicrometer thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching behavior in two types, P-I and P-II, of submicrometer Pac-man-shaped Ni/sub 80/Fe/sub 20/ magnetic elements are studied using both magnetic force microscopy (MFM) and numerical simulation. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation-driven switching is replaced by quasi-coherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic Configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms.

  • Magnetization switching dynamics depending on as-patterned Magnetization state in magnetic thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, J. Ho, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching dynamics of submicrometer "Pac-man"-shaped Ni/sub 80/Fe/sub 20/ elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy (MFM), magnetooptic Kerr effect (MOKE), and micromagnetic simulations. It was found that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct Magnetization Configurations and magnetic switching mechanisms (in low frequencies), even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal. Fast Magnetization reversal is, however, found to be slightly dependent on as-patterned domain Configurations. For all elements investigated, the fast reversal leads to very complex nonequilibrium domain Configurations.

  • Magnetic switching depending on as-patterned Magnetization state in Pac-man shaped Ni80Fe20 submicron elements
    Journal of Applied Physics, 2004
    Co-Authors: B. R. Pujada, M H Park, Y K Hong, J. Svendsen, Karsten Chipeniuk, Byoung-chul Choi, D W Erickson
    Abstract:

    Magnetization Configuration and magnetic switching of submiron “Pac-man” shaped Ni80Fe20 elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy, magneto-optical Kerr effect, and micromagnetic simulations. Experimental measurements and modeling analysis clearly demonstrate that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct Magnetization Configurations and magnetic switching mechanisms, even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal.

  • Magnetization Configuration and switching behavior of submicron nife elements pac man shape
    Applied Physics Letters, 2003
    Co-Authors: M H Park, Y K Hong, D W Erickson, B C Choi
    Abstract:

    Two types of submicron permalloy element, namely Pac-man, were investigated by a magnetic force microscope for Magnetization Configuration and switching behaviors. Two distinct domain Configurations, bidomain for Pac-man type I and single domain for Pac-man type II, were observed in arrays of Pac-man elements. The domain Configuration depends on the slot angle for the Pac-man type I, but is independent of the slot angle for the Pac-man type II. Array of Pac-man elements with a slot angle of 180° shows the highest switching field and the narrowest switching field distribution, as compared to rectangular and hexagonal elements of the same overall dimensions.

Y K Hong - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation Study of Magnetization Precession Dynamics in Submicrometer Elliptical Ni$_80$Fe$_20$Thin-Film Elements
    IEEE Transactions on Magnetics, 2006
    Co-Authors: B C Choi, Y K Hong, J. Jabal, Q.f. Xiao, K.j. Hass, G.w. Donohoe
    Abstract:

    Nonequilibrium Magnetization Configuration and magnetic switching behavior are studied using micromagnetic modeling. In particular, it is found that coherent rotation and Magnetization ringing in submicrometer Ni80Fe20 elements can be controlled by adjusting the axis-ratio of the ellipse, the thickness, and the angle of the magnetic field pulse with respect to the axis of elliptical elements. For the element with 400-nm-long axis, 200-nm-short axis, and 4.7-nm thickness, the nonuniform distribution of Magnetization results from a strong in-plane, nonuniform deMagnetization field during Magnetization precession. The simulation results indicate that uniformity in the distribution of the Magnetization during reversal is improved by reducing the length of the short axis from 200 nm to 112 nm, and reducing the thickness of the thin film from 4.7 to 3.2 nm. The modification in the geometric Configuration of the element is found to effectively suppress the Magnetization ringing

  • Micromagnetic domain structures and Magnetization switching mechanism in submicron thin film elements
    2005 IEEE International Magnetics Conference (INTERMAG), 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Experimental and numerical micromagnetic studies of the Magnetization Configuration and switching process in Pac-man (PM) shaped Ni/sub 80/Fe/sub 20/ samples with different geometries defined by the variation of the slot angle were presented. Scanning electron microscope images of patterned PM-I and PM-II magnetic elements were shown. These permalloy films were sputter deposited and their magnetic Configurations were measured. The results concluded that vortex core formation and vortex-driven complex Magnetization reversal can be effectively suppressed by modifying the slot angles. The hysteresis loops and domain Configurations during the reversal implied that PM-II elements with large slot angles were more suitable for magnetic random access memory (MRAM) applications.

  • Micromagnetic domain structures and Magnetization switching mechanism in submicrometer thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, B. R. Pujada, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching behavior in two types, P-I and P-II, of submicrometer Pac-man-shaped Ni/sub 80/Fe/sub 20/ magnetic elements are studied using both magnetic force microscopy (MFM) and numerical simulation. It was found that a slight variation in the shape of the elements has a striking influence on the internal magnetic structures and switching field distribution. In particular, the vortex-formation-driven switching is replaced by quasi-coherent reversal by removing the central core part at the center of element. The sensitive dependence of remanent magnetic Configuration and switching behavior on sample geometry is discussed in terms of the competition between the exchange and demagnetizing energy terms.

  • Magnetization switching dynamics depending on as-patterned Magnetization state in magnetic thin-film elements
    IEEE Transactions on Magnetics, 2005
    Co-Authors: B C Choi, M H Park, Y K Hong, J. Ho, G.w. Donohoe
    Abstract:

    Magnetization Configuration and magnetic switching dynamics of submicrometer "Pac-man"-shaped Ni/sub 80/Fe/sub 20/ elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy (MFM), magnetooptic Kerr effect (MOKE), and micromagnetic simulations. It was found that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct Magnetization Configurations and magnetic switching mechanisms (in low frequencies), even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal. Fast Magnetization reversal is, however, found to be slightly dependent on as-patterned domain Configurations. For all elements investigated, the fast reversal leads to very complex nonequilibrium domain Configurations.

  • Magnetic switching depending on as-patterned Magnetization state in Pac-man shaped Ni80Fe20 submicron elements
    Journal of Applied Physics, 2004
    Co-Authors: B. R. Pujada, M H Park, Y K Hong, J. Svendsen, Karsten Chipeniuk, Byoung-chul Choi, D W Erickson
    Abstract:

    Magnetization Configuration and magnetic switching of submiron “Pac-man” shaped Ni80Fe20 elements with conventional and modified (i.e., elongated) geometry have been studied using magnetic force microscopy, magneto-optical Kerr effect, and micromagnetic simulations. Experimental measurements and modeling analysis clearly demonstrate that the sensitive interplay between exchange, demagnetizing, and shape anisotropy energies leads to distinct Magnetization Configurations and magnetic switching mechanisms, even though the geometric shape of elements is only slightly modified. In a particular case, such as 40% elongated element, vortex-driven magnetic switching is replaced by well-defined coherent reversal.

Jacob Linder - One of the best experts on this subject based on the ideXlab platform.

  • meissner effect probing of odd frequency triplet pairing in superconducting spin valves
    Physical Review B, 2014
    Co-Authors: Mohammad Alidoust, Klaus Halterman, Jacob Linder
    Abstract:

    Superconducting correlations which are long-ranged in magnetic systems have attracted much attention due to their spin-polarization properties and potential use in spintronic devices. Whereas experiments have demonstrated the slow decay of such correlations, it has proven more difficult to obtain a smoking gun signature of their odd-frequency character which is responsible, e.g. for their gapless behavior. We here demonstrate that the magnetic susceptibility response of a normal metal in contact with a superconducting spin-valve provides precisely this signature, namely in form of an anomalous "positive" Meissner effect which may be tuned back to a conventional "negative" Meissner response simply by altering the Magnetization Configuration of the spin-valve.