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Yoshishige Suzuki - One of the best experts on this subject based on the ideXlab platform.
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underlayer material influence on electric field controlled Perpendicular Magnetic Anisotropy in cofeb mgo Magnetic tunnel junctions
Physical Review B, 2015Co-Authors: Yoichi Shiota, Hitoshi Kubota, Takayuki Nozaki, Witold Skowronski, Duong D Lam, Kay Yakushiji, Akio Fukushima, Shinji Yuasa, Yoshishige SuzukiAbstract:We study the dependence of the Perpendicular Magnetic Anisotropy on the underlayer material in Magnetic tunnel junction. Using several different 4d and 5d metals we identify an optimal seed layer in terms of high Anisotropy, low mixing, and high thermal stability. In such systems we investigate the tunability of the Anisotropy by means of electric fields. Especially, by using W as the underlayer of the CoFeB/MgO/CoFeB trilayer we could obtain good thermal stability that allows for annealing in the temperatures up to $450{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, which results in high Perpendicular Anisotropy.
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spin orbit torque in a bulk Perpendicular Magnetic Anisotropy pd fepd mgo system
Scientific Reports, 2015Co-Authors: Hwangrae Lee, Yoichi Shiota, Kyujoon Lee, Jaehun Cho, Youngha Choi, Chunyeol You, Myunghwa Jung, Frederic Bonell, Shinji Miwa, Yoshishige SuzukiAbstract:Spin-orbit torques, including the Rashba and spin Hall effects, have been widely observed and investigated in various systems. Since interesting spin-orbit torque (SOT) arises at the interface between heavy nonMagnetic metals and ferroMagnetic metals, most studies have focused on the ultra-thin ferroMagnetic layer with interface Perpendicular Magnetic Anisotropy. Here, we measured the effective longitudinal and transverse fields of bulk Perpendicular Magnetic Anisotropy Pd/FePd (1.54 to 2.43 nm)/MgO systems using harmonic methods with careful correction procedures. We found that in our range of thicknesses, the effective longitudinal and transverse fields are five to ten times larger than those reported in interface Perpendicular Magnetic Anisotropy systems. The observed magnitude and thickness dependence of the effective fields suggest that the SOT do not have a purely interfacial origin in our samples.
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opposite signs of voltage induced Perpendicular Magnetic Anisotropy change in cofeb mgo junctions with different underlayers
Applied Physics Letters, 2013Co-Authors: Yoichi Shiota, Frederic Bonell, Shinji Miwa, Teruya Shinjo, Norikazu Mizuochi, Yoshishige SuzukiAbstract:We report a voltage-induced Perpendicular Magnetic Anisotropy (PMA) change in sputter-deposited Ta|CoFeB|MgO and Ru|CoFeB|MgO junctions. The PMA change is quantitatively evaluated by the field dependence of the tunneling magnetoresistance for various bias voltages. We find that both the sign and amplitude of the voltage effect depend on the underlayer, Ta or Ru, below the CoFeB layer. The rf voltage-induced ferroMagnetic resonance spectra also support the underlayer-material-dependent direction of the voltage torque. The present study shows that the underlayer is one of the key parameters for controlling the voltage effect.
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large change in Perpendicular Magnetic Anisotropy induced by an electric field in fepd ultrathin films
Applied Physics Letters, 2011Co-Authors: Frederic Bonell, Yoichi Shiota, S Murakami, Takayuki Nozaki, Teruya Shinjo, Yoshishige SuzukiAbstract:The Magnetic properties of FePd ultrathin films and their variation under the influence of an electric field are investigated by magneto-optical Kerr effect (MOKE) measurements. L10-ordered FePd shows a spin reorientation transition when varying the thickness. The easy axis of magnetization is found to be normal to the plane at thicknesses above 9 monolayers (MLs) and in-plane below 9 ML. The coercive field, the Perpendicular Magnetic Anisotropy and the MOKE signal at saturation vary with the applied electric field. The sensitivity of the interface Magnetic Anisotropy is estimated to be 602 fJ/V m.
Yoichi Shiota - One of the best experts on this subject based on the ideXlab platform.
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underlayer material influence on electric field controlled Perpendicular Magnetic Anisotropy in cofeb mgo Magnetic tunnel junctions
Physical Review B, 2015Co-Authors: Yoichi Shiota, Hitoshi Kubota, Takayuki Nozaki, Witold Skowronski, Duong D Lam, Kay Yakushiji, Akio Fukushima, Shinji Yuasa, Yoshishige SuzukiAbstract:We study the dependence of the Perpendicular Magnetic Anisotropy on the underlayer material in Magnetic tunnel junction. Using several different 4d and 5d metals we identify an optimal seed layer in terms of high Anisotropy, low mixing, and high thermal stability. In such systems we investigate the tunability of the Anisotropy by means of electric fields. Especially, by using W as the underlayer of the CoFeB/MgO/CoFeB trilayer we could obtain good thermal stability that allows for annealing in the temperatures up to $450{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, which results in high Perpendicular Anisotropy.
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spin orbit torque in a bulk Perpendicular Magnetic Anisotropy pd fepd mgo system
Scientific Reports, 2015Co-Authors: Hwangrae Lee, Yoichi Shiota, Kyujoon Lee, Jaehun Cho, Youngha Choi, Chunyeol You, Myunghwa Jung, Frederic Bonell, Shinji Miwa, Yoshishige SuzukiAbstract:Spin-orbit torques, including the Rashba and spin Hall effects, have been widely observed and investigated in various systems. Since interesting spin-orbit torque (SOT) arises at the interface between heavy nonMagnetic metals and ferroMagnetic metals, most studies have focused on the ultra-thin ferroMagnetic layer with interface Perpendicular Magnetic Anisotropy. Here, we measured the effective longitudinal and transverse fields of bulk Perpendicular Magnetic Anisotropy Pd/FePd (1.54 to 2.43 nm)/MgO systems using harmonic methods with careful correction procedures. We found that in our range of thicknesses, the effective longitudinal and transverse fields are five to ten times larger than those reported in interface Perpendicular Magnetic Anisotropy systems. The observed magnitude and thickness dependence of the effective fields suggest that the SOT do not have a purely interfacial origin in our samples.
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opposite signs of voltage induced Perpendicular Magnetic Anisotropy change in cofeb mgo junctions with different underlayers
Applied Physics Letters, 2013Co-Authors: Yoichi Shiota, Frederic Bonell, Shinji Miwa, Teruya Shinjo, Norikazu Mizuochi, Yoshishige SuzukiAbstract:We report a voltage-induced Perpendicular Magnetic Anisotropy (PMA) change in sputter-deposited Ta|CoFeB|MgO and Ru|CoFeB|MgO junctions. The PMA change is quantitatively evaluated by the field dependence of the tunneling magnetoresistance for various bias voltages. We find that both the sign and amplitude of the voltage effect depend on the underlayer, Ta or Ru, below the CoFeB layer. The rf voltage-induced ferroMagnetic resonance spectra also support the underlayer-material-dependent direction of the voltage torque. The present study shows that the underlayer is one of the key parameters for controlling the voltage effect.
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large change in Perpendicular Magnetic Anisotropy induced by an electric field in fepd ultrathin films
Applied Physics Letters, 2011Co-Authors: Frederic Bonell, Yoichi Shiota, S Murakami, Takayuki Nozaki, Teruya Shinjo, Yoshishige SuzukiAbstract:The Magnetic properties of FePd ultrathin films and their variation under the influence of an electric field are investigated by magneto-optical Kerr effect (MOKE) measurements. L10-ordered FePd shows a spin reorientation transition when varying the thickness. The easy axis of magnetization is found to be normal to the plane at thicknesses above 9 monolayers (MLs) and in-plane below 9 ML. The coercive field, the Perpendicular Magnetic Anisotropy and the MOKE signal at saturation vary with the applied electric field. The sensitivity of the interface Magnetic Anisotropy is estimated to be 602 fJ/V m.
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Voltage-induced Perpendicular Magnetic Anisotropy change in Magnetic tunnel junctions
Applied Physics Letters, 2010Co-Authors: Tatsuo Nozaki, TAKAO SHINJO, Yoichi Shiota, M Shiraishi, Y. SuzukiAbstract:A voltage-induced Perpendicular Magnetic Anisotropy change in an ultrathin FeCo layer was observed in an epitaxialMagnetic tunnel junction(MTJ) structure. A spin-transfer induced ferroMagnetic resonance measurement technique was used under various bias voltage applications to evaluate the Anisotropy change. From the peak frequency shifts, we could estimate that a surface Magnetic Anisotropy change of 15 μ J / m 2 was induced by an electric field application of 400 mV/nm in the MTJ with a 0.5 nm thick FeCo layer. The realization of voltage-induced Anisotropy changes in an MTJ structure should have a large impact on the development of electric-field driven spintronic devices.
B Dieny - One of the best experts on this subject based on the ideXlab platform.
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Anatomy of electric field control of Perpendicular Magnetic Anisotropy at Fe/MgO interfaces
Physical Review B: Condensed Matter and Materials Physics, 2016Co-Authors: F. Ibrahim, B Dieny, H. X. Yang, A. Hallal, M. ChshievAbstract:The charge-mediated effect of electric field on the Perpendicular Magnetic Anisotropy (PMA) of Fe/MgO interfaces is investigated using first-principles calculations. We present an approach by discussing this effect in relation to the intrinsic dipole field existing at the Fe/MgO interface. A firm correlation between the PMA and the interfacial dipole is established and further verified in the absence of an applied electric field. The on-site projected PMA analysis not only elucidates that the effect of electric field on the PMA extends beyond the interfacial Fe layer, but also shows that the second Fe layer carries the largest contribution to the effect. This observation is interpreted in relation to the orbital hybridization changes induced by applying an electric field.
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anatomy of Perpendicular Magnetic Anisotropy in fe mgo Magnetic tunnel junctions first principles insight
Physical Review B, 2013Co-Authors: Ali Hallal, Hongxin Yang, B Dieny, Mairbek ChshievAbstract:Using first-principles calculations, we elucidate microscopic mechanisms of Perpendicular Magnetic Anisotropy (PMA) in Fe/MgO Magnetic tunnel junctions through evaluation of orbital and layer resolved contributions into the total Anisotropy value. It is demonstrated that the origin of the large PMA values is far beyond simply considering the hybridization between Fe-$3d$ and O-$2p$ orbitals at the interface between the metal and the insulator. Onsite projected analysis shows that the Anisotropy energy is not localized at the interface but it rather propagates into the bulk showing an attenuating oscillatory behavior which depends on orbital character of contributing states and interfacial conditions. Furthermore, it is found in most situations that states with ${d}_{yz(xz)}$ and ${d}_{{z}^{2}}$ character tend always to maintain the PMA while those with ${d}_{xy}$ and ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$ character tend to favor the in-plane Anisotropy. It is also found that while MgO thickness has no influence on PMA, the calculated Perpendicular Magnetic Anisotropy oscillates as a function of Fe thickness with a period of 2 ML and reaches a maximum value of 3.6 mJ/m${}^{2}$.
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enhancement of Perpendicular Magnetic Anisotropy through reduction of co pt interdiffusion in co pt multilayers
Applied Physics Letters, 2012Co-Authors: S Bandiera, R C Sousa, B Rodmacq, B DienyAbstract:We demonstrate that the effective Magnetic Anisotropy of sputtered (Co/Pt) multilayers can be doubled by limiting the interdiffusion occurring at Co/Pt interfaces. We present a way to decrease the interdiffusion by inserting an ultra-thin Cu layer at or near the Co/Pt interfaces. When such a material is sputtered on Co prior to the Pt deposition, the Perpendicular Magnetic Anisotropy, as well as the thermal stability, is enhanced for Co layer thicknesses smaller than 1 nm. This is of great interest for out-of-plane magnetized spintronic devices which require high Perpendicular Magnetic Anisotropy for down-size scalability reasons together with a free layer as thin as possible to reduce the writing energy when switched by spin transfer torque.
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asymmetric interfacial Perpendicular Magnetic Anisotropy in pt co pt trilayers
IEEE Magnetics Letters, 2011Co-Authors: S Bandiera, B Rodmacq, R R Sousa, B DienyAbstract:An asymmetry in the interfacial anisotropies of Pt/Co and Co/Pt interfaces was observed in Pt/Co/Pt sputtered trilayers, the interfacial Anisotropy arising from the bottom Pt/Co interface being significantly higher than that from the top Co/Pt one. Interdiffusion at the top interface is believed to be the main factor for this asymmetry. It dramatically decreases the Anisotropy of the stack when the cobalt layer is thinner than 1 nm. By introducing ultrathin layers of materials immiscible with Co and acting as a diffusion barrier at the Co/Pt interface, the effective Anisotropy can be doubled in this low Co thickness range. This is of great interest for spintronic devices, particularly for out-of-plane magnetized magnetoresistive random access memory structures that require high Perpendicular Magnetic Anisotropy when their lateral dimensions are reduced below 45 nm.
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first principles investigation of the very large Perpendicular Magnetic Anisotropy at fe mgo and co mgo interfaces
Physical Review B, 2011Co-Authors: Hongxin Yang, Aurélien Manchon, B Dieny, Mairbek Chshiev, J H Lee, K H ShinAbstract:The Perpendicular Magnetic Anisotropy (PMA) arising at the interface between ferroMagnetic transition metals and metallic oxides are investigated via first-principles calculations. In this work very large values of PMA up to 3 erg/cm$^2$ at Fe$|$MgO interfaces are reported in agreement with recent experiments. The origin of PMA is attributed to overlap between O-$p_z$ and transition metal $d_{z^2}$ orbitals hybridized with $d_{xz(yz)}$ orbitals with stronger spin-orbit coupling induced splitting around the Fermi level for Perpendicular magnetization orientation. Furthemore, it is shown that the PMA value weakens in case of over- or underoxidation when oxygen $p_z$ and transition metal $d_{z^2}$ orbitals overlap is strongly affected by disorder, in agreement with experimental observations in Magnetic tunnel junctions.
Jan Vogel - One of the best experts on this subject based on the ideXlab platform.
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Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy
Physical Review Letters, 2012Co-Authors: Jan Vogel, Nicolas Rougemaille, Stéphane Auffret, Bernard Rodmacq, Marlio Bonfim, Olivier Boulle, Ioan Mihai Miron, Gilles Gaudin, J. C. Cezar, Fausto SirottiAbstract:Domain wall motion induced by nanosecond current pulses in nanostripes with Perpendicular Magnetic Anisotropy (Pt/Co/AlO$_x$) is shown to exhibit negligible inertia. Time-resolved Magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low 'mass' of these domain walls is attributed to the combination of their narrow width and high damping parameter $\alpha$. Such a small inertia should allow accurate control of domain wall motion, by tuning the duration and amplitude of the current pulses.
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high domain wall velocities induced by current in ultrathin pt co alox wires with Perpendicular Magnetic Anisotropy
Applied Physics Letters, 2008Co-Authors: Th Moore, Jan Vogel, Stéphane Auffret, Ioan Mihai Miron, Gilles Gaudin, G Serret, B Rodmacq, Alain Schuhl, S Pizzini, M BonfimAbstract:Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with Perpendicular Magnetic Anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j≤1.5×1012 A/m2), the DW motion obeys a creep law. At higher current density (j=1.8×1012 A/m2), zero-field average DW velocities up to 130±10 m/s were recorded.
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high domain wall velocities induced by current in ultrathin pt co alox wires with Perpendicular Magnetic Anisotropy
arXiv: Other Condensed Matter, 2008Co-Authors: Th Moore, Jan Vogel, Stéphane Auffret, Ioan Mihai Miron, Gilles Gaudin, G Serret, B Rodmacq, Alain Schuhl, S Pizzini, M BonfimAbstract:Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with Perpendicular Magnetic Anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer-scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j less than or equal to 1.5 x 10^12 A/m^2), the DW motion obeys a creep law. At higher current density (j = 1.8 x 10^12 A/m^2), zero-field average DW velocities up to 130 +/- 10 m/s were recorded.
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X-Ray Analysis of Oxygen-induced Perpendicular Magnetic Anisotropy in Pt/Co/AlOx trilayer
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: Aurélien Manchon, Stefania Pizzini, Jan Vogel, Vojtech Uhlir, Lucien Lombard, Clarisse Ducruet, Stéphane Auffret, Bernard Rodmacq, Bernard Dieny, Michael HochstrasserAbstract:X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx trilayers to investigate the role of Co oxidation in the Perpendicular Magnetic Anisotropy of the Co/AlOx interface. It is observed that high temperature annealing modifies the Magnetic properties of the Co layer, inducing an enhancement of the Perpendicular Magnetic Anisotropy. The microscopic structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements. It is shown that annealing enhances the amount of interfacial oxide, which may be at the origin of a strong Perpendicular Magnetic Anisotropy.
Stéphane Auffret - One of the best experts on this subject based on the ideXlab platform.
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Direct Observation of Massless Domain Wall Dynamics in Nanostripes with Perpendicular Magnetic Anisotropy
Physical Review Letters, 2012Co-Authors: Jan Vogel, Nicolas Rougemaille, Stéphane Auffret, Bernard Rodmacq, Marlio Bonfim, Olivier Boulle, Ioan Mihai Miron, Gilles Gaudin, J. C. Cezar, Fausto SirottiAbstract:Domain wall motion induced by nanosecond current pulses in nanostripes with Perpendicular Magnetic Anisotropy (Pt/Co/AlO$_x$) is shown to exhibit negligible inertia. Time-resolved Magnetic microscopy during current pulses reveals that the domain walls start moving, with a constant speed, as soon as the current reaches a constant amplitude, and no or little motion takes place after the end of the pulse. The very low 'mass' of these domain walls is attributed to the combination of their narrow width and high damping parameter $\alpha$. Such a small inertia should allow accurate control of domain wall motion, by tuning the duration and amplitude of the current pulses.
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high domain wall velocities induced by current in ultrathin pt co alox wires with Perpendicular Magnetic Anisotropy
Applied Physics Letters, 2008Co-Authors: Th Moore, Jan Vogel, Stéphane Auffret, Ioan Mihai Miron, Gilles Gaudin, G Serret, B Rodmacq, Alain Schuhl, S Pizzini, M BonfimAbstract:Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with Perpendicular Magnetic Anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j≤1.5×1012 A/m2), the DW motion obeys a creep law. At higher current density (j=1.8×1012 A/m2), zero-field average DW velocities up to 130±10 m/s were recorded.
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high domain wall velocities induced by current in ultrathin pt co alox wires with Perpendicular Magnetic Anisotropy
arXiv: Other Condensed Matter, 2008Co-Authors: Th Moore, Jan Vogel, Stéphane Auffret, Ioan Mihai Miron, Gilles Gaudin, G Serret, B Rodmacq, Alain Schuhl, S Pizzini, M BonfimAbstract:Current-induced domain wall (DW) displacements in an array of ultrathin Pt/Co/AlOx wires with Perpendicular Magnetic Anisotropy have been directly observed by wide field Kerr microscopy. DWs in all wires in the array were driven simultaneously and their displacement on the micrometer-scale was controlled by the current pulse amplitude and duration. At the lower current densities where DW displacements were observed (j less than or equal to 1.5 x 10^12 A/m^2), the DW motion obeys a creep law. At higher current density (j = 1.8 x 10^12 A/m^2), zero-field average DW velocities up to 130 +/- 10 m/s were recorded.
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X-Ray Analysis of Oxygen-induced Perpendicular Magnetic Anisotropy in Pt/Co/AlOx trilayer
Journal of Magnetism and Magnetic Materials, 2008Co-Authors: Aurélien Manchon, Stefania Pizzini, Jan Vogel, Vojtech Uhlir, Lucien Lombard, Clarisse Ducruet, Stéphane Auffret, Bernard Rodmacq, Bernard Dieny, Michael HochstrasserAbstract:X-ray spectroscopy measurements have been performed on a series of Pt/Co/AlOx trilayers to investigate the role of Co oxidation in the Perpendicular Magnetic Anisotropy of the Co/AlOx interface. It is observed that high temperature annealing modifies the Magnetic properties of the Co layer, inducing an enhancement of the Perpendicular Magnetic Anisotropy. The microscopic structural properties are analyzed via X-ray Absorption Spectroscopy, X-ray Magnetic Circular Dichroism and X-ray Photoelectron Spectroscopy measurements. It is shown that annealing enhances the amount of interfacial oxide, which may be at the origin of a strong Perpendicular Magnetic Anisotropy.
