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  • 1.
    Kravets, A. F.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Polishchuk, Dmytro M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Dzhezherya, Yu. I.
    Tovstolytkin, A. I.
    Golub, V. O.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Anisotropic magnetization relaxation in ferromagnetic multilayers with variable interlayer exchange coupling2016In: PHYSICAL REVIEW B, ISSN 2469-9950, Vol. 94, no 6, article id 064429Article in journal (Refereed)
    Abstract [en]

    The ferromagnetic resonance (FMR) linewidth and its anisotropy in F-1/f/F-2/AF multilayers, where spacer f has a low Curie point compared to the strongly ferromagnetic F-1 and F-2, is investigated. The role of the interlayer exchange coupling in magnetization relaxation is determined experimentally by varying the thickness of the spacer. It is shown that stronger interlayer coupling via thinner spacers enhances the microwave energy exchange between the outer ferromagnetic layers, with themagnetization of F-2 exchange dragged by the resonance precession in F-1. A weaker mirror effect is also observed: the magnetization of F-1 can be exchange dragged by the precession in F-2, which leads to antidamping and narrower FMR linewidths. A theory is developed to model the measured data, which allows separating various contributions to the magnetic relaxation in the system. Key physical parameters, such as the interlayer coupling constant, in-plane anisotropy of the FMR linewidth, and dispersion of the magnetic anisotropy fields, are quantified. These results should be useful for designing high-speed magnetic nanodevices based on thermally assisted switching.

  • 2.
    Kravets, Anatolii
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Gomonay, O. V.
    Polishchuk, Dmytr
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tykhonenko-Polishchuk, Yu.O.
    Polek, T. I.
    Tovstolytkin, A. I.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056312Article in journal (Refereed)
    Abstract [en]

    In this work we focus on magnetic relaxation in Mn80Ir20(12 nm)/Cu(6 nm)/Py(dF) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM) multilayers with different thickness of the ferromagnetic permalloy layer. An effective FM-AFM interaction mediated via the conduction electrons in the nonmagnetic Cu spacer - the spin-pumping effect - is detected as an increase in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of the resonant magnetic field. We further find experimentally that the spin-pumping-induced contribution to the linewidth is inversely proportional to the thickness of the Py layer. We show that this thickness dependence likely originates from the dissipative dynamics of the free and localized spins in the AFM layer. The results obtained could be used for tailoring the dissipative properties of spintronic devices incorporating antiferromagnetic layers.

  • 3.
    Kravets, Anatolii
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Polishchuk, Dmytro
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Pashchenko, V. A.
    Tovstolytkin, A. I.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Current-driven thermo-magnetic switching in magnetic tunnel junctions2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, no 26, article id 262401Article in journal (Refereed)
    Abstract [en]

    We investigate switching of magnetic tunnel junctions (MTJs) driven by the thermal effect of the transport current through the junctions. The switching occurs in a specially designed composite free layer, which acts as one of the MTJ electrodes, and is due to a current-driven ferro-to-paramagnetic Curie transition with the associated exchange decoupling within the free layer leading to magnetic reversal. We simulate the current and heat propagation through the device and show how heat focusing can be used to improve the power efficiency. The Curie-switch MTJ demonstrated in this work has the advantage of being highly tunable in terms of its operating temperature range, conveniently to or just above room temperature, which can be of technological significance and competitive with the known switching methods using spin-transfer torques.

  • 4.
    Kravets, Anatolii
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Tovstolytkin, A. I.
    Dzhezherya, Yu I.
    Polishchuk, Dmytro
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Kozak, I. M.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Spin dynamics in a Curie-switch2015In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 27, no 44, article id 446003Article in journal (Refereed)
    Abstract [en]

    Ferromagnetic resonance properties of F-1/f/F-2/AF multilayers, where weakly ferromagnetic spacer f is sandwiched between strongly ferromagnetic layers F-1 and F-2, with F-1 being magnetically soft and F-2-magnetically hard due to exchange pinning to antiferromagnetic layer AF, are investigated. Spacer-mediated exchange coupling is shown to strongly affect the resonance fields of both F-1 and F-2 layers. Our theoretical calculations as well as measurements show that the key magnetic parameters of the spacer, which govern the ferromagnetic resonance in F-1/f/F-2/AF, are the magnetic exchange length (Lambda), effective saturation magnetization at T = 0 (m(0)) and effective Curie temperature (T-C(eff)). The values of these key parameters are deduced from the experimental data for multilayers with f = NixCu100-x, for the key ranges in the Ni-concentration (x = 54 divided by 70 at. %) and spacer thickness (d = 3 divided by 6 nm). The results obtained provide a deeper insight into thermally-controlled spin precession and switching in magnetic nanostructures, with potential applications in spin-based oscillators and memory devices.

  • 5.
    Polishchuk, Dmytr
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tykhonenko-Polishchuk, Yu. O.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Holmgren, Erik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Kravets, Anatolii
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Thermally induced antiferromagnetic exchange in magnetic multilayers2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 10, article id 104427Article in journal (Refereed)
    Abstract [en]

    We demonstrate sharp thermally induced switching between ferromagnetic and antiferromagnetic RKKY ( Ruderman-Kittel-Kasuya-Yosida) exchange in a spin-valve with the spacer incorporating a thin diluted ferromagnetic layer as the core. We illustrate the mechanism behind the effect as being due to a change in the effective thickness of the spacer induced by the Curie transition into its paramagnetic state. The ability to switch between ferromagnetic and antiferromagnetic states in a magnetic multilayer by a slight change in temperature may lead to new types of spin-thermoelectronic devices for use in such applications as memory or oscillators.

  • 6.
    Polishchuk, Dmytr
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. Inst Magnetism NAS & MES Ukraine.
    Tykhonenko-Polishchuk, Yu. O.
    Kravets, Anatolii
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tovstolytkin, A. I.
    Dzhezherya, Yu. I.
    Pogorily, A. M.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Ferromagnetic resonance in nanostructures with temperature-controlled interlayer interaction2016In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 42, no 9, p. 761-767Article in journal (Refereed)
    Abstract [en]

    This study is a comprehensive analysis of a multilayer F-1/f(d)/F-2pin structure's magnetic resonance properties, wherein F-1 and F-2pin are the free and exchange-coupled strong magnetic layers, and f is the weakly magnetic layer with a Curie point in the room temperature region. Depending on the magnetic state of the spacer f (ferromagnetic or paramagnetic) the exchange interaction between the F-2 and F-2pin layers becomes a function of the temperature, which opens up opportunities for practical applications. The obtained results show that the interlayer exchange coupling can be enhanced by decreasing the thickness of the spacer d, or by lowering the temperature. Strengthening the exchange coupling leads to a stronger manifestation of unidirectional anisotropy in the ferromagnetic resonance layer F-1, as well as to a broadening of the resonance line that is atypical for thin films. The observed features are analyzed in the context of comparing the effects of two different natures: the influence of the spacer d and the influence of the temperature. Thus, the behavior of changes to the unidirectional anisotropy remains the same given variation of both the thickness of the spacer and the temperature. However the broadening of the magnetic resonance line is more sensitive to changes in the interlayer interaction caused by variation of d, and is less susceptible to changes caused by temperature.

  • 7.
    Polishchuk, Dmytr
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tykhonenko-Polishchuk, Yu.O.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Kravets, Anatolii
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. National Academy of Sciences of Ukraine, Ukraine.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Thermal switching of indirect interlayer exchange in magnetic multilayers2017In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 118, no 3, article id 37006Article in journal (Refereed)
    Abstract [en]

    We propose a magnetic multilayer layout, in which the indirect exchange coupling (IEC also known as RKKY) can be switched on and off by a slight change in temperature. We demonstrate such on/off IEC switching in a Fe/Cr/FeCr-based system and obtain thermal switching widths as small as 10-20 K, essentially in any desired temperature range, including at or just above room temperature. These results add a new dimension of tunable thermal control to IEC in magnetic nanostructures, highly technological in terms of available materials and operating physical regimes.

  • 8.
    Polishchuk, Dmytro M.
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. NAS of Ukraine, Ukraine.
    Kravets, Anatolii F.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. NAS of Ukraine, Ukraine.
    Tykhonenko-Polishchuk, Yu.O.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Tovstolytkin, A. I.
    Korenivski, Vladislav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Ferromagnetic resonance and interlayer exchange coupling in magnetic multilayers with compositional gradients2017In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056307Article in journal (Refereed)
    Abstract [en]

    Ferromagnetic resonance (FMR) in magnetic multilayers of type F1/f/F2, where two strongly ferromagnetic layers F1 and F2 are separated by a weakly magnetic spacer f with a compositional gradient along its thickness, is investigated. The method allows to detect the weak signal from the spacer in additional to the more pronounced and readily measured signal from the outer strongly-magnetic layers, and thereby study the properties of the spacer as well as the interlayer exchange interaction it mediates. Variable temperature FMR measurements, especially near the relevant Curie points, reveal a rich set of properties of the exchange interactions in the system. The obtained results are useful for designing and optimizing nanostructures with thermally-controlled magnetic properties.

1 - 8 of 8
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  • ieee
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