Asymmetric Magnetization Switching in Perpendicular Magnetic Tunnel Junctions: Role of the Synthetic Antiferromagnet’s Fringe Field

Lavanant, M.; Vallobra, Pierre; Watelot, S. Petit; Lomakin, Vitaliy; Kent, Andrew D.; Sun, J. Z.; Mangin, Stéphane

doi:10.1103/physrevapplied.11.034058

Cited by 14 publications

(8 citation statements)

References 32 publications

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“…The signature of this higher order anisotropy term is not always visible in the collinear geometry but clearly shows up once the field is applied away from the normal to the plane of the sample. Such second order anisotropy contribution is similar to that reported previously [17,18,[22][23][24][25].…”

Section: Introductionsupporting

confidence: 91%

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

et al. 2017

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International audienceExperimental measurements performed on MgO-based perpendicular magnetic tunnel junctions show a strong dependence of the stability voltage-field diagrams as a function of the direction of the magnetic field with respect to the plane of the sample. When the magnetic field is applied in-plane, systematic nonlinear phase boundaries are observed for various lateral sizes. The simulation results based on the phenomenological Landau-Lifshitz-Gilbert equation including the in-plane and out-of-plane spin transfer torques are consistent with the measurements if a second-order anisotropy contribution is considered. Furthermore, performing the stability analysis in linear approximation allowed us to analytically extract the critical switching voltage at zero temperature in the presence of an in-plane field. This study indicates that in the noncollinear geometry investigations are suitable to detect the presence of the second-order term in the anisotropy. Such higher order anisotropy term can yield an easy-cone anisotropy which reduces the thermal stability factor but allows for more reproducible spin transfer torque switching due to a reduced stochasticity of the switching. As a result, the energy per write event decreases much faster than the thermal stability factor as the second-order anisotropy becomes more negative. Easy-cone anisotropy can be useful for fast-switching spin transfer torque magnetic random access memories provided the thermal stability can be maintained above the required value for a given memory specification

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Section: Introductionsupporting

confidence: 91%

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

et al. 2017

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“…This highlights the importance of investigating the magnetic properties of the free layer to better understand and predict the switching dynamics. It is particularly important to include the effect of stray fields of polarizer layer that can have stabilizing or destabilizing effects on the free layer magnetization depending on the initial magnetic configuration [23]. We conclude that a strong exchange interaction is required to ensure fast, energy efficient, and coherent spin torque switching of the free layer.…”

Section: Discussionmentioning

confidence: 94%

Spin-torque switching mechanisms of perpendicular magnetic tunnel junction nanopillars

Mohammadi

Kent

2021

Applied Physics Letters

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Understanding the magnetization dynamics induced by spin-transfer torques in perpendicularly magnetized magnetic tunnel junction nanopillars and its dependence on material parameters is critical to optimizing device performance. Here we present a micromagnetic study of spin-torque switching in a diskshaped element as a function of the free layer's exchange constant and disk diameter. The switching is shown to generally occur by: 1) growth of the magnetization precession amplitude in the element center; 2) an instability in which the reversing region moves to the disk edge, forming a magnetic domain wall; and 3) the motion of the domain wall across the element. For large diameters and small exchange, step 1 leads to a droplet with a fully reversed core that experiences a drift instability (step 2). While in the opposite case (small diameters and large exchange), the central region of the disk is not fully reversed before step 2 occurs. The origin of the micromagnetic structure is shown to be the disk's non-uniform demagnetization field. Faster, more coherence and energy efficient switching occur with larger exchange and smaller disk diameters, showing routes to increase device performance.

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“…Interestingly, the SFD is much broader for B on (26 mT) than for B off (5 mT) in the single-particle PT MCD measurements, whereas they are similar (both 10 mT) for the SQUID measurements. This can be speculatively explained by the dipole fields in the AP configuration, as schematically shown in Figure S13, and by the role of residual nucleation embryos in the reversal mechanism of on- and off-switching. − When NPs switch from AP to P state ( B on ), the dipole fields of the two CoB layers repel each other, leading to a canting of the magnetization at the edge of NPs, which, in turn, assists domain nucleation. In the P to AP switching ( B off ), the dipole fields are aligned and do not contribute to the nucleation process.…”

Section: Resultsmentioning

confidence: 99%

Optical Monitoring of the Magnetization Switching of Single Synthetic-Antiferromagnetic Nanoplatelets with Perpendicular Magnetic Anisotropy

Adhikari

Wang

et al. 2023

ACS Photonics

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Synthetic antiferromagnetic nanoplatelets (NPs) with a large perpendicular magnetic anisotropy (SAF-PMA NPs) have a large potential in future local mechanical torque-transfer applications for e.g., biomedicine. However, the mechanisms of magnetization switching of these structures at the nanoscale are not well understood. Here, we have used a simple and relatively fast single-particle optical technique that goes beyond the diffraction limit to measure photothermal magnetic circular dichroism (PT MCD). This allows us to study the magnetization switching as a function of applied magnetic field of single 122 nm diameter SAF-PMA NPs with a thickness of 15 nm. We extract and discuss the differences between the switching field distributions of large ensembles of NPs and of single NPs. In particular, single-particle PT MCD allows us to address the spatial and temporal heterogeneity of the magnetic switching fields of the NPs at the single-particle level. We expect this new insight to help understand better the dynamic torque transfer, e.g., in biomedical and microfluidic applications.

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Asymmetric Magnetization Switching in Perpendicular Magnetic Tunnel Junctions: Role of the Synthetic Antiferromagnet’s Fringe Field

Cited by 14 publications

References 32 publications

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

Stability phase diagram of a perpendicular magnetic tunnel junction in noncollinear geometry

Spin-torque switching mechanisms of perpendicular magnetic tunnel junction nanopillars

Optical Monitoring of the Magnetization Switching of Single Synthetic-Antiferromagnetic Nanoplatelets with Perpendicular Magnetic Anisotropy

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