The Experts below are selected from a list of 33657 Experts worldwide ranked by ideXlab platform
R A Buhrman - One of the best experts on this subject based on the ideXlab platform.
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enhancement of perpendicular Magnetic anisotropy and transmission of spin hall effect induced spin currents by a hf spacer layer in w hf cofeb mgo layer structures
Applied Physics Letters, 2014Co-Authors: Chifeng Pai, D C Ralph, Minhhai Nguyen, Carina Belvin, L H Vilelaleao, R A BuhrmanAbstract:We report that strong perpendicular Magnetic anisotropy of the ferroMagnetic layer in a W/CoFeB/MgO multilayer structure can be established by inserting a Hf layer as thin as 0.25 nm between the W and CoFeB layers. The Hf spacer also allows transmission of spin currents generated by an in-plane charge current in the W layer to apply strong spin torque on the CoFeB, thereby enabling current-driven Magnetic Switching. The antidamping-like and field-like components of the spin torque exerted on a 1 nm CoFeB layer are of comparable magnitudes in this geometry. Both components originate from the spin Hall effect in the underlying W layer.
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Magnetic Switching by spin torque from the spin hall effect
arXiv: Materials Science, 2011Co-Authors: Luqiao Liu, D C Ralph, O J Lee, T J Gudmundsen, R A BuhrmanAbstract:The spin Hall effect (SHE) generates spin currents within nonMagnetic materials. Previously, studies of the SHE have been motivated primarily to understand its fundamental origin and magnitude. Here we demonstrate, using measurement and modeling, that in a Pt/Co bilayer with perpendicular Magnetic anisotropy the SHE can produce a spin transfer torque that is strong enough to efficiently rotate and reversibly switch the Co magnetization, thereby providing a new strategy both to understand the SHE and to manipulate magnets. We suggest that the SHE torque can have a similarly strong influence on current-driven Magnetic domain wall motion in Pt/ferromagnet multilayers. We estimate that in optimized devices the SHE torque can switch Magnetic moments using currents comparable to those in Magnetic tunnel junctions operated by conventional spin-torque Switching, meaning that the SHE can enable Magnetic memory and logic devices with similar performance but simpler architecture than the current state of the art.
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spin transfer effects in nanoscale Magnetic tunnel junctions
Applied Physics Letters, 2004Co-Authors: G D Fuchs, I N Krivorotov, N C Emley, R A Buhrman, D C Ralph, P M Braganca, E M Ryan, S I Kiselev, J C Sankey, Jordan A. KatineAbstract:We report measurements of Magnetic Switching and steady-state Magnetic precession driven by spin-polarized currents in nanoscale Magnetic tunnel junctions with low-resistance, <5Ωμm2, barriers. The current densities required for Magnetic Switching are similar to values for all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven Switching can occur at voltages that are high enough to quench the tunnel magnetoresistance, demonstrating that the current remains spin polarized at these voltages.
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spin transfer effects in nanoscale Magnetic tunnel junctions
arXiv: Materials Science, 2004Co-Authors: G D Fuchs, Jordan A. Katine, I N Krivorotov, N C Emley, D C Ralph, P M Braganca, E M Ryan, S I Kiselev, J C Sankey, R A BuhrmanAbstract:We report measurements of Magnetic Switching and steady-state Magnetic precession driven by spin-polarized currents in nanoscale Magnetic tunnel junctions with low-resistance, < 5 Ohm-micron-squared, barriers. The current densities required for Magnetic Switching are similar to values for all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven Switching can occur at voltages that are high enough to quench the tunnel magnetoresistance, demonstrating that the current remains spin-polarized at these voltages.
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quantitative study of magnetization reversal by spin polarized current in Magnetic multilayer nanopillars
Physical Review Letters, 2002Co-Authors: F J Albert, N C Emley, D C Ralph, E B Myers, R A BuhrmanAbstract:We have studied Magnetic Switching by spin-polarized currents and also the magnetoresistance in sub-100-nm-diam thin-film Co/Cu/Co nanostructures, with the current flowing perpendicular to the plane of the films. By independently varying the thickness of all three layers and measuring the change of the Switching currents, we test the theoretical models for spin-transfer Switching. In addition, the changes in the Switching current and magnetoresistance as a function of the Cu layer thickness give two independent measurements of the room-temperature spin-diffusion length in Cu.
O Hellwig - One of the best experts on this subject based on the ideXlab platform.
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accumulative Magnetic Switching of ultrahigh density recording media by circularly polarized light
Physical review applied, 2016Co-Authors: Y K Takahashi, O Hellwig, R Medapalli, S Kasai, J Wang, Kunie Ishioka, S H Wee, K Hono, Eric E FullertonAbstract:In addition to heat-assisted Magnetic recording (HAMR), all-optical Switching (AOS) is an attractive technology for the next generation of ultrahigh-density, ultrafast, ultralow-power digital storage. The authors demonstrate cumulative magnetization Switching in granular Fe-Pt-C due to multiple pulses of circularly polarized light. While this base process is statistical, adding a modest external Magnetic field allows deterministic Switching, which shows that this form of AOS can aid writing in a HAMR-like recording process.
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accumulative Magnetic Switching of ultra high density recording media by circularly polarized light
arXiv: Mesoscale and Nanoscale Physics, 2016Co-Authors: Y Takahashi, O Hellwig, R Medapalli, S Kasai, J Wang, Kunie Ishioka, S H Wee, K Hono, Eric E FullertonAbstract:Manipulation of the magnetization by external energies other than Magnetic field, such as spin-polarized current1-4, electric voltage5,6 and circularly polarized light7-11 gives a paradigm shift in Magnetic nanodevices. Magnetization control of ferroMagnetic materials only by circularly polarized light has received increasing attention both as a fundamental probe of the interactions of light and magnetism but also for future high-density Magnetic recording technologies. Here we show that for granular FePt films, designed for ultrahigh-density recording, the optical Magnetic Switching by circularly polarized light is an accumulative effect from multiple optical pulses. We further show that deterministic Switching of high anisotropy materials by the combination of circularly polarized light and modest external Magnetic fields, thus revealing a pathway towards technological implementation.
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origin of Magnetic Switching field distribution in bit patterned media based on pre patterned substrates
Applied Physics Letters, 2011Co-Authors: Bastian Pfau, C M Gunther, Erik Guehrs, Thomas Hauet, Hongxin Yang, L Vinh, D Yaney, R Rick, S Eisebitt, O HellwigAbstract:Using a combination of synchrotron radiation based Magnetic imaging and high-resolution transmission electron microscopy we reveal systematic correlations between the Magnetic Switching field and the internal nanoscale structure of individual islands in bit patterned media fabricated by Co/Pd-multilayer deposition onto pre-patterned substrates. We find that misaligned grains at the island periphery are a common feature independent of the island Switching field, while irregular island shapes and misaligned grains specifically extending into the center of an island are systematically correlated with a reduced island reversal field.
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bit patterned media based on block copolymer directed assembly with narrow Magnetic Switching field distribution
Applied Physics Letters, 2010Co-Authors: O Hellwig, Thomas Hauet, D Yaney, Joan K Bosworth, E Dobisz, Dan S Kercher, Gabriel Zeltzer, J D Risnerjamtgaard, Ricardo RuizAbstract:Electron-beam (E-beam) directed assembly, which combines the long-range phase and placement registration of e-beam lithography with the sharp dot size and spacing uniformity of block copolymer self assembly, is considered highly promising for fabricating templates that meet the tight Magnetic specifications required for write synchronization in bit patterned media Magnetic recording systems. In our study, we show that this approach also yields a narrower Magnetic Switching field distribution (SFD) than e-beam patterning or block copolymer self-assembly alone. We demonstrate that the pattern uniformity, i.e., island diameter and placement distributions are also important for achieving tight Magnetic SFDs.
M Helm - One of the best experts on this subject based on the ideXlab platform.
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dependence of all optical Magnetic Switching on the sublattice magnetization orientation in tb fe thin films
IEEE International Magnetics Conference, 2015Co-Authors: Alexander Hassdenteufel, Christian Schubert, Johannes Schmidt, Peter Richter, D R T Zahn, Georgeta Salvan, M Helm, Rudolf Bratschitsch, Manfred AlbrechtAbstract:We demonstrate that the direction of all-optical Switching (AOS) in rare-earth transition-metal (RE-TM) alloy Tb-Fe thin films depends on the orientation of the sublattice magnetization and not on the direction of the resulting net magnetization.
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dependence of all optical Magnetic Switching on the sublattice magnetization orientation in tb fe thin films
Applied Physics Letters, 2014Co-Authors: Alexander Hassdenteufel, Christian Schubert, Johannes Schmidt, Peter Richter, D R T Zahn, Georgeta Salvan, M HelmAbstract:We demonstrate that the direction of all-optical Switching (AOS) in rare-earth transition-metal (RE-TM) alloy Tb-Fe thin films depends on the orientation of the sublattice magnetization and not on the direction of the resulting net magnetization. For this purpose, we investigated the AOS ability for a sample dominated by the Fe sublattice magnetization (Tb24Fe76) and another dominated by the Tb sublattice (Tb30Fe70). This finding of the sublattice dependence of AOS contributes to the understanding of Switching in RE-TM multilayered thin films and heterostructures.
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thermally assisted all optical helicity dependent Magnetic Switching in amorphous fe 100 x tb x alloy films
Advanced Materials, 2013Co-Authors: Alexander Hassdenteufel, Christian Schubert, M Helm, Manfred Albrecht, Birgit Hebler, A Liebig, Martin Teich, Martin Aeschlimann, Rudolf BratschitschAbstract:All-optical Switching (AOS) in ferriMagnetic Fe(100-x)Tb(x) alloys is presented. AOS is witnessed below, above, and in samples without a Magnetic compensation point. It is found that AOS is associated with laser heating up to the Curie temperature and intimately linked to a low remanent sample magnetization. Above a threshold magnetization of 220 emu/cc helicity dependent AOS is replaced by pure thermal demagnetization.
J Z Sun - One of the best experts on this subject based on the ideXlab platform.
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effect of subvolume excitation and spin torque efficiency on Magnetic Switching
Physical Review B, 2011Co-Authors: J Z Sun, Michael C Gaidis, Eugene J Osullivan, D W Abraham, J Nowak, P L Trouilloud, Stephen L Brown, W J Gallagher, R P Robertazzi, Daniel C WorledgeAbstract:Recently developed Magnetic tunnel junctions with full perpendicular magnetization that are spin-torque switchable allow for quantitative comparison of spin-torque Switching statistics with a macrospin model. For typical devices above 50 nm in lateral size, the comparison suggests the presence of subvolume Magnetic excitations which often dominate the Switching process and which degrade the spin-torque Switching efficiency. A simple model of subvolume spin-torque-driven Magnetic Switching is presented to account for the experimental observations. The origin of the subvolume thermal excitation is traced to a competition between the macrospin fluctuation within a simple uniaxial anisotropy potential and that of thermal magnon excitation. The subvolume excitation problem highlights the importance of improving the Magnetic exchange stiffness of the junction free layer, and the reduction of junction lateral sizes below 50 nm where an improved spin-torque efficiency is seen as the Switching dynamics cross over to a more macrospin-like process.
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a three terminal spin torque driven Magnetic switch
Applied Physics Letters, 2009Co-Authors: J Z Sun, Michael C Gaidis, Eugene J Osullivan, Eric A Joseph, D W Abraham, J Nowak, P L Trouilloud, Stephen L Brown, Daniel C Worledge, W J GallagherAbstract:A three-terminal spin-torque-driven Magnetic switch is experimentally demonstrated. The device uses nonlocal spin current and spin accumulation as the main mechanism for current-driven Magnetic Switching. It separates the current-induced write operation from that of a Magnetic tunnel junction based read. The write current only passes through metallic structures, improving device reliability. The device structure makes efficient use of lithography capabilities, important for robust process integration.
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high bias backhopping in nanosecond time domain spin torque switches of mgo based Magnetic tunnel junctions
Journal of Applied Physics, 2009Co-Authors: J Z Sun, Michael C Gaidis, Eugene J Osullivan, J Nowak, P L Trouilloud, Stephen L Brown, Daniel C WorledgeAbstract:For CoFeB∕MgO-based Magnetic tunnel junctions, the Switching probability has an unusual dependence on bias voltage V and bias Magnetic field H for bias voltage pulse durations t long enough to allow thermally activated reversal. At high junction bias close to 1V, the probability of Magnetic Switching in spin-torque-driven switches sometimes appears to decrease. This is shown to be due to a backhopping behavior occurring at high bias, and it is asymmetric in bias voltage, being more pronounced in the bias direction for antiparallel-to-parallel spin-torque switch, i.e., in the direction of electrons tunneling into the free layer. This asymmetry hints at processes involving hot electrons within the free-layer nanomagnet.
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thermally activated sweep rate dependence of Magnetic Switching field in nanostructured current perpendicular spin valves
Journal of Magnetism and Magnetic Materials, 2002Co-Authors: J Z Sun, L Chen, Yuri Suzuki, Stuart S P Parkin, R H KochAbstract:Abstract We report on the thermal-activation nature of Magnetic Switching in Magnetic nanostructures, using the junction magnetoresistance of a current-perpendicular Magnetic spin-valve device as a probe. A spin-valve junction structure was fabricated using electron-beam lithography. A sweep-rate-dependent Magnetic Switching field was obtained in the quasi-static limit. Results confirm the predictions of a single-domain thermal activation model. The scaling relation between the Magnetic field sweep rate, the Magnetic Switching field, and the sample size is verified for sample dimensions of 0.1×0.2 μm 2 .
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current driven Magnetic Switching in manganite trilayer junctions
Journal of Magnetism and Magnetic Materials, 1999Co-Authors: J Z SunAbstract:Abstract A current-driven Switching of Magnetic state is observed in manganite trilayer junctions. The Switching current threshold I c depends on applied Magnetic field. The Switching is due to the transfer of spin-momentum from spin-polarized carriers to a ferroMagnetic cluster situated between the electrodes. A model developed based on the spin-momentum transfer process quantitatively describes the experimental observation.
D C Ralph - One of the best experts on this subject based on the ideXlab platform.
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enhancement of perpendicular Magnetic anisotropy and transmission of spin hall effect induced spin currents by a hf spacer layer in w hf cofeb mgo layer structures
Applied Physics Letters, 2014Co-Authors: Chifeng Pai, D C Ralph, Minhhai Nguyen, Carina Belvin, L H Vilelaleao, R A BuhrmanAbstract:We report that strong perpendicular Magnetic anisotropy of the ferroMagnetic layer in a W/CoFeB/MgO multilayer structure can be established by inserting a Hf layer as thin as 0.25 nm between the W and CoFeB layers. The Hf spacer also allows transmission of spin currents generated by an in-plane charge current in the W layer to apply strong spin torque on the CoFeB, thereby enabling current-driven Magnetic Switching. The antidamping-like and field-like components of the spin torque exerted on a 1 nm CoFeB layer are of comparable magnitudes in this geometry. Both components originate from the spin Hall effect in the underlying W layer.
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Magnetic Switching by spin torque from the spin hall effect
arXiv: Materials Science, 2011Co-Authors: Luqiao Liu, D C Ralph, O J Lee, T J Gudmundsen, R A BuhrmanAbstract:The spin Hall effect (SHE) generates spin currents within nonMagnetic materials. Previously, studies of the SHE have been motivated primarily to understand its fundamental origin and magnitude. Here we demonstrate, using measurement and modeling, that in a Pt/Co bilayer with perpendicular Magnetic anisotropy the SHE can produce a spin transfer torque that is strong enough to efficiently rotate and reversibly switch the Co magnetization, thereby providing a new strategy both to understand the SHE and to manipulate magnets. We suggest that the SHE torque can have a similarly strong influence on current-driven Magnetic domain wall motion in Pt/ferromagnet multilayers. We estimate that in optimized devices the SHE torque can switch Magnetic moments using currents comparable to those in Magnetic tunnel junctions operated by conventional spin-torque Switching, meaning that the SHE can enable Magnetic memory and logic devices with similar performance but simpler architecture than the current state of the art.
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spin transfer effects in nanoscale Magnetic tunnel junctions
Applied Physics Letters, 2004Co-Authors: G D Fuchs, I N Krivorotov, N C Emley, R A Buhrman, D C Ralph, P M Braganca, E M Ryan, S I Kiselev, J C Sankey, Jordan A. KatineAbstract:We report measurements of Magnetic Switching and steady-state Magnetic precession driven by spin-polarized currents in nanoscale Magnetic tunnel junctions with low-resistance, <5Ωμm2, barriers. The current densities required for Magnetic Switching are similar to values for all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven Switching can occur at voltages that are high enough to quench the tunnel magnetoresistance, demonstrating that the current remains spin polarized at these voltages.
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spin transfer effects in nanoscale Magnetic tunnel junctions
arXiv: Materials Science, 2004Co-Authors: G D Fuchs, Jordan A. Katine, I N Krivorotov, N C Emley, D C Ralph, P M Braganca, E M Ryan, S I Kiselev, J C Sankey, R A BuhrmanAbstract:We report measurements of Magnetic Switching and steady-state Magnetic precession driven by spin-polarized currents in nanoscale Magnetic tunnel junctions with low-resistance, < 5 Ohm-micron-squared, barriers. The current densities required for Magnetic Switching are similar to values for all-metallic spin-valve devices. In the tunnel junctions, spin-transfer-driven Switching can occur at voltages that are high enough to quench the tunnel magnetoresistance, demonstrating that the current remains spin-polarized at these voltages.
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quantitative study of magnetization reversal by spin polarized current in Magnetic multilayer nanopillars
Physical Review Letters, 2002Co-Authors: F J Albert, N C Emley, D C Ralph, E B Myers, R A BuhrmanAbstract:We have studied Magnetic Switching by spin-polarized currents and also the magnetoresistance in sub-100-nm-diam thin-film Co/Cu/Co nanostructures, with the current flowing perpendicular to the plane of the films. By independently varying the thickness of all three layers and measuring the change of the Switching currents, we test the theoretical models for spin-transfer Switching. In addition, the changes in the Switching current and magnetoresistance as a function of the Cu layer thickness give two independent measurements of the room-temperature spin-diffusion length in Cu.
