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A O Adeyeye - One of the best experts on this subject based on the ideXlab platform.
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reprogrammable magnonic band structure of layered Permalloy cu Permalloy nanowires
Physical Review B, 2018Co-Authors: G Gubbiotti, X Zhou, Zahra Haghshenasfard, M G Cottam, A O AdeyeyeAbstract:Reprogrammability of magnonic band structure in layered Permalloy/Cu/Permalloy nanowires is demonstrated to depend on the relative orientation of the two layers magnetization. By using Brillouin light spectroscopy, we show that when the layers are aligned parallel two dispersive modes, with positive and negative group velocity, are observed while when the magnetic layers are aligned anti-parallel, only one dispersive mode, with positive group velocity, is detected. Our findings are successfully compared and interpreted in terms of a microscopic (Hamiltonian-based) method. An explanation for the observed behavior can be attributed to mode-mixing (or hybridization) effect when the two magnetic layers are aligned anti-parallel. This work opens the path to magnetic field-controlled reconfigurable magnonic crystals with multi-modal frequency transmission characteristics.
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plasmon assisted high reflectivity and strong magneto optical kerr effect in Permalloy gratings
Applied Physics Letters, 2013Co-Authors: Nikita Kostylev, A O Adeyeye, Ivan S Maksymov, Sergey Samarin, Mikhail Kostylev, James WilliamsAbstract:We demonstrate experimentally a strong plasmon-assisted enhancement of the transverse magneto-optical Kerr effect in Permalloy gratings. The enhanced transverse magneto-optical Kerr effect is accompanied by an increased grating reflectivity with the maximum of enhancement being correlated with plasmonic Fano resonances. This correlation was confirmed by an intuitive Fano model and also through full-vectorial optical simulations. Simultaneously high reflectivity and transverse magneto-optical Kerr effect as well as narrowest ferromagnetic resonance linewidth and vanishing anisotropy make Permalloy nanostructures attractive for applications in spintronics and nano-optics such as, for example, all-optical excitation of propagating spin waves and spectral tuning of optical nanoantennas.
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interfacial magnetization dynamics of a bi component magnonic crystal comprising contacting ferromagnetic nanostripes
Journal of Applied Physics, 2012Co-Authors: Chyuansheng Lin, M G Cottam, V L Zhang, M H Kuok, S Jain, H S Lim, Zhikui Wang, A O AdeyeyeAbstract:An investigation of the interfacial magnetization dynamics of a magnonic crystal comprising alternating, contacting cobalt and Permalloy nanostripes is reported. Recently measured spin-wave dispersion data of the crystal in its ferromagnetic and antiferromagnetic phases are interpreted in terms of the effective spin pinning at its cobalt-Permalloy interfaces based on generalized Guslienko-Slavin boundary conditions. Calculations using a macroscopic theory well reproduce the experimental data. Numerically generated mode profiles reveal considerable effective pinnings at the interfaces. The obtained pinning parameters have values significantly larger than the values calculated at the lateral edges of individual stripes, suggesting that the strong interfacial coupling, reported in our previous study, contributes significantly to the effective pinning at the interfaces between adjacent stripes.
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ferromagnetic and antiferromagnetic spin wave dispersions in a dipole exchange coupled bi component magnonic crystal
Applied Physics Letters, 2011Co-Authors: V L Zhang, A O Adeyeye, Z K Wang, S C Ng, M H Kuok, S Jain, Michael G CottamAbstract:The magnon dispersion relations of the ferromagnetic and antiferromagnetic phases in a dipole-exchange coupled one-dimensional magnonic crystal comprising alternating cobalt and Permalloy nanostripes have been mapped by Brillouin spectroscopy. To elucidate the magnetization dynamics at the interfaces between stripes, the experimental data are analyzed based on a macroscopic theory under Hoffmann-type boundary conditions. Good agreement is obtained between theory and experiment for both the ferromagnetic and antiferromagnetic phases. Results suggest the existence of strong exchange coupling across the cobalt-Permalloy interfaces, comparable with the exchange coupling within each component material.
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magnetization reversal and anisotropic magnetoresistance behavior in bicomponent antidot nanostructures
Applied Physics Letters, 2010Co-Authors: D Tripathy, P Vavassori, J M Porro, A O Adeyeye, N SinghAbstract:We report on the magnetic properties and anisotropic magnetoresistance behavior of engineered bicomponent array of “holes” with alternating diameters embedded in a continuous Permalloy film. We observed that the magnetization reversal is significantly altered when compared to a homogeneous array of antidots, and exhibits strong dependence on the Permalloy thickness. Our results demonstrate that the use of two antidot sublattices greatly enhances the parameters available for engineering the behavior of antidot nanostructures.
D C Ralph - One of the best experts on this subject based on the ideXlab platform.
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spin orbit torques in nbse2 Permalloy bilayers
Nano Letters, 2018Co-Authors: M H D Guimaraes, David Macneill, Gregory M. Stiehl, Neal Reynolds, D C RalphAbstract:We present measurements of current-induced spin–orbit torques generated by NbSe2, a fully metallic transition-metal dichalcogenide material, made using the spin-torque ferromagnetic resonance (ST-FMR) technique with NbSe2/Permalloy bilayers. In addition to the out-of-plane Oersted torque expected from current flow in the metallic NbSe2 layer, we also observe an in-plane antidamping torque with torque conductivity σS ≈ 103 (ℏ/2e)(Ωm)−1 and indications of a weak field-like contribution to the out-of-plane torque oriented opposite to the Oersted torque. Furthermore, in some samples we also measure an in-plane field-like torque with the form m × z, where m is the Permalloy magnetization direction and z is perpendicular to the sample plane. The size of this component varies strongly between samples and is not correlated with the NbSe2 thickness. A torque of this form is not allowed by the bulk symmetries of NbSe2 but is consistent with symmetry breaking by a uniaxial strain that might result during device ...
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time resolved spin torque switching and enhanced damping in Permalloy cu Permalloy spin valve nanopillars
Physical Review Letters, 2006Co-Authors: N C Emley, D C Ralph, I N Krivorotov, O Ozatay, A G F Garcia, J C Sankey, R A BuhrmanAbstract:We report time-resolved measurements of current-induced reversal of a free magnetic layer in Permalloy/Cu/Permalloy elliptical nanopillars at temperatures T=4.2 K to 160 K. Comparison of the data to Landau-Lifshitz-Gilbert macrospin simulations of the free layer switching yields numerical values for the spin torque and the Gilbert damping parameters as functions of T. The damping is strongly T dependent, which we attribute to the presence of an antiferromagnetic oxide layer around the perimeter of the Permalloy free layer. This adventitious antiferromagnetic oxide can have a major impact on spin-torque phenomena.
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spin transfer excitations of Permalloy nanopillars for large applied currents
Physical Review B, 2005Co-Authors: S I Kiselev, N C Emley, I N Krivorotov, A G F Garcia, J C Sankey, R A Buhrman, D C RalphAbstract:Using measurements of the spectra of microwave-frequency resistance oscillations, we determine the roomtemperature phase diagram of magnetic excitations caused by torques from dc spin-polarized currents in thin Permalloy/copper/thick Permalloy multilayer samples. We extend the measurements to larger values of current than have been reported previously. We find several additional modes that we are able to identify with motion of the thick magnetic layer as well as the thin one. Peaks in the microwave spectra at multiple frequencies suggest that spatially nonuniform dynamical states can be important in some circumstances. We compare the experimental phase diagram with simple theoretical models and achieve a good qualitative agreement.
A D Kent - One of the best experts on this subject based on the ideXlab platform.
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sub nanosecond switching in a cryogenic spin torque spin valve memory element with a dilute Permalloy free layer
Applied Physics Letters, 2019Co-Authors: Laura Rehm, Volker Sluka, Graham Rowlands, Minhhai Nguyen, Thomas A Ohki, A D KentAbstract:We present a study of pulsed current switching characteristics of spin-valve nanopillars with in-plane magnetized dilute Permalloy and undiluted Permalloy free layers in the ballistic regime at low temperatures. The dilute Permalloy free layer device switches much faster: the characteristic switching time for a Permalloy (Ni0.83Fe0.17) free layer device is 1.18 ns, while that for a dilute Permalloy ([Ni0.83Fe0.17]0.6Cu0.4) free layer device is 0.475 ns. A ballistic macrospin model can capture the data trends with a reduced spin-torque asymmetry parameter, reduced spin polarization, and increased Gilbert damping for the dilute Permalloy free layer relative to the Permalloy devices. Our study demonstrates that reducing the magnetization of the free layer increases the switching speed while greatly reducing the switching energy and shows a promising route toward even lower power magnetic memory devices compatible with superconducting electronics.We present a study of pulsed current switching characteristics of spin-valve nanopillars with in-plane magnetized dilute Permalloy and undiluted Permalloy free layers in the ballistic regime at low temperatures. The dilute Permalloy free layer device switches much faster: the characteristic switching time for a Permalloy (Ni0.83Fe0.17) free layer device is 1.18 ns, while that for a dilute Permalloy ([Ni0.83Fe0.17]0.6Cu0.4) free layer device is 0.475 ns. A ballistic macrospin model can capture the data trends with a reduced spin-torque asymmetry parameter, reduced spin polarization, and increased Gilbert damping for the dilute Permalloy free layer relative to the Permalloy devices. Our study demonstrates that reducing the magnetization of the free layer increases the switching speed while greatly reducing the switching energy and shows a promising route toward even lower power magnetic memory devices compatible with superconducting electronics.
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sub nanosecond switching in a cryogenic spin torque spin valve memory element with a dilute Permalloy free layer
arXiv: Applied Physics, 2019Co-Authors: Laura Rehm, Volker Sluka, Graham Rowlands, Minhhai Nguyen, Thomas A Ohki, A D KentAbstract:We present a study of the pulsed current switching characteristics of spin-valve nanopillars with in-plane magnetized dilute Permalloy and undiluted Permalloy free layers in the ballistic regime at low temperature. The dilute Permalloy free layer device switches much faster: the characteristic switching time for a Permalloy free (Ni0.83Fe0.17) layer device is 1.18 ns, while that for a dilute Permalloy ([Ni0.83Fe0.17]0.6Cu0.4) free layer device is 0.475 ns. A ballistic macrospin model can capture the data trends with a reduced spin torque asymmetry parameter, reduced spin polarization and increased Gilbert damping for the dilute Permalloy free layer relative to the Permalloy devices. Our study demonstrates that reducing the magnetization of the free layer increases the switching speed while greatly reducing the switching energy and shows a promising route toward even lower power magnetic memory devices compatible with superconducting electronics.
Felix Casanova - One of the best experts on this subject based on the ideXlab platform.
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spin diffusion length of Permalloy using spin absorption in lateral spin valves
arXiv: Mesoscale and Nanoscale Physics, 2019Co-Authors: Edurne Sagasta, Yasutomo Omori, Miren Isasa, Luis E Hueso, Felix CasanovaAbstract:We employ the spin absorption technique in lateral spin valves to extract the spin diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the spin diffusion length with conductivity of Py is observed, evidencing that Elliott-Yafet is the dominant spin relaxation mechanism in Permalloy. Completing the data set with additional data found in literature, we obtain $\lambda_{Py}= (0.91\pm 0.04) (f\Omega m^2)/\rho_{Py}$.
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spin diffusion length of Permalloy using spin absorption in lateral spin valves
Applied Physics Letters, 2017Co-Authors: Edurne Sagasta, Yasutomo Omori, Miren Isasa, Luis E Hueso, Felix CasanovaAbstract:We employ the spin absorption technique in lateral spin valves to extract the spin diffusion length of Permalloy (Py) as a function of temperature and resistivity. A linear dependence of the spin diffusion length with the conductivity of Py is observed, evidencing that the Elliott-Yafet mechanism is the dominant spin relaxation mechanism in Permalloy. Completing the dataset with additional data found in the literature, we obtain λPy = (0.91 ± 0.04) (fΩm2)/ρPy.
Teruya Shinjo - One of the best experts on this subject based on the ideXlab platform.
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in plane spin orbit torque magnetization switching and its detection using the spin rectification effect at subgigahertz frequencies
Physical Review B, 2020Co-Authors: Motomi Aoki, Ei Shigematsu, Ryo Ohshima, Syuta Honda, Teruya Shinjo, Masashi Shiraishi, Masayuki Matsushima, Yuichiro AndoAbstract:In-plane magnetization reversal of a Permalloy/platinum bilayer was detected using the spin rectification effect. Using a subgigahertz microwave frequency to excite spin-torque ferromagnetic resonance (ST-FMR) in the bilayer induces two discrete DC voltages around an external static magnetic field of 0 mT. These discrete voltages depend on the magnetization directions of the Permalloy and enable detection of the in-plane magnetization reversal. The threshold current density for the magnetization reversal is around $10--20\phantom{\rule{0.16em}{0ex}}\mathrm{MA}/\mathrm{c}{\mathrm{m}}^{2}$, the same order as for known spin-orbit torque switching with in-plane magnetization materials. The magnitude of the signal is the same or larger than that of the typical ST-FMR signal; that is, detection of magnetization switching is highly sensitive in spite of deviation from the optimal ST-FMR condition. The proposed method is applicable to a simple device structure even for a small ferromagnetic electrode with a width of 100 nm.
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Inplane spin orbit torque magnetization switching and its detection using the spin rectification effect at sub-GHz frequencies
arXiv: Materials Science, 2020Co-Authors: Motomi Aoki, Ei Shigematsu, Ryo Ohshima, Syuta Honda, Teruya Shinjo, Masashi Shiraishi, Yuichiro AndoAbstract:Inplane magnetization reversal of a Permalloy/platinum bilayer was detected using the spin rectification effect. Using a sub GHz microwave frequency to excite spin torque ferromagnetic resonance (ST FMR) in the bilayer induces two discrete DC voltages around an external static magnetic field of 0 mT. These discrete voltages depend on the magnetization directions of the Permalloy and enable detection of the inplane magnetization reversal. The threshold current density for the magnetization reversal is from 10 to 20 MA/cm^2, the same order as for known spin orbit torque (SOT) switching with in-plane magnetization materials. The magnitude of the signal is the same or larger than that of the typical ST FMR signal; that is, detection of magnetization switching is highly sensitive in spite of deviation from the optimal ST-FMR condition. The proposed method is applicable to a simple device structure even for a small ferromagnetic electrode with a width of 100 nm.
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mfm study of magnetic vortex cores in circular Permalloy dots behavior in external field
Journal of Magnetism and Magnetic Materials, 2002Co-Authors: T Okuno, K Shigeto, Teruo Ono, Ko Mibu, Teruya ShinjoAbstract:Abstract In a circular dot of Permalloy with an appropriate size, a vortex structure with perpendicular (turned-up) magnetization at the core is realized. The existence of the perpendicular magnetization spot has been confirmed and the direction of the magnetization, up or down, has been determined by magnetic force microscopy (MFM) for Permalloy dots with the diameter of 0.1–1 μm. The switching field of turned-up magnetization is determined by applying external fields perpendicularly and in tilted directions to the plane. By comparing the MFM results and the magnetization curves measured by a SQUID magnetometer, the switching process of turned-up magnetization is argued.
