Microstructural origin of switching field distribution in patterned Co∕Pd multilayer nanodots

Lau, June W.; McMichael, Robert D.; Chung, Seok-Hwan; Rantschler, James; Parekh, Vishal; Litvinov, Dmitri

doi:10.1063/1.2822439

Cited by 75 publications

(62 citation statements)

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“…As a consequence, the larger the number of ͑100͒ and ͑110͒ grains per dot is, the lower is the switching field. 7,8 Note that the reversal fields of the BPM dots are systematically lower than the effective anisotropy, even before irradiation ͓Fig. 3͑a͔͒.…”

Section: -mentioning

confidence: 99%

“…3,4 The SFD has multiple origins but intrinsic growth defects leading to anisotropy distribution has been shown to be a dominant one. [5][6][7][8] These defects include misorientated grains, grain boundaries, distribution of easy axis angle, variations in lattice stress, and variations in thicknesses or interface roughness in multilayers. Two recent investigations 7,8 indicate that misorientated crystalline grains are the major microstructural origin of SFD in ͑111͒ textured ͓Co/Pd͔ multilayers.…”

mentioning

confidence: 99%

“…[5][6][7][8] These defects include misorientated grains, grain boundaries, distribution of easy axis angle, variations in lattice stress, and variations in thicknesses or interface roughness in multilayers. Two recent investigations 7,8 indicate that misorientated crystalline grains are the major microstructural origin of SFD in ͑111͒ textured ͓Co/Pd͔ multilayers. However, identifying the effects of these correlated structural defects remains an issue and key quest toward achieving lower SFD.…”

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confidence: 99%

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Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

Hauet¹,

Hellwig

Park³

et al. 2011

Applied Physics Letters

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International audienceWe have used ion irradiation to tune switching field and switching field distribution ͑SFD͒ in polycrystalline Co/Pd multilayer-based bit pattern media. Light He + ion irradiation strongly decreases perpendicular magnetic anisotropy amplitude due to Co/Pd interface intermixing, while the granular structure, i.e., the crystalline anisotropy, remains unchanged. In dot arrays, the anisotropy reduction leads to a decrease in coercivity ͑H C ͒ but also to a strong broadening of the normalized SFD/ H C ͑in percentage͒, since the relative impact of misaligned grains is enhanced. Our experiment thus confirms the major role of misorientated grains in SFD of nanodevice arrays. Today a major research effort in magnetism is targeted toward achieving ultrahigh density data storage with nano-scale magnets. Spin-transfer magnetic random access memory ͑spin-RAM͒ and bit patterned media ͑BPM͒ technologies are currently part of the most promising media. The implementation of both of these technologies relies on achieving in-detail physical understanding and control of the magnetization reversal mechanism in each nanoscopic individual bit to ensure reproducibility of the bit properties in order to avoid write errors. Perpendicular magnetic anisotropy ͑PMA͒ materials, such as polycrystalline Co/Pd, Co/Pt, and Co/Ni multilayers, are believed to be promising materials for both spin-RAM and BPM applications. 1–4 Indeed, they have a well defined high amplitude uniaxial anisotropy that provides good thermal stability while offering low critical current in spin-transfer devices 2 and tunable switching fields in BPM.

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Section: -mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

Hauet¹,

Hellwig

Park³

et al. 2011

Applied Physics Letters

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“…Variations in island reversal fields are assumed to be induced by variations of the magnitude or direction of the local anisotropy, such as originating from island size, shape, composition, and (crystalline) structure as well as localized strain, corrupted island edges, or misaligned grains. [3][4][5][6][7] In a recent study, Lau et al found that islands with a low switching field (easy switchers) do predominantly contain a "trigger" grain larger than the exchange length with in-plane [100] vector, whereas islands with high switching field (stubborn or hard switchers) do not. 7 The magnetic nanodots in Ref.…”

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confidence: 99%

“…[3][4][5][6][7] In a recent study, Lau et al found that islands with a low switching field (easy switchers) do predominantly contain a "trigger" grain larger than the exchange length with in-plane [100] vector, whereas islands with high switching field (stubborn or hard switchers) do not. 7 The magnetic nanodots in Ref. 7 were fabricated by transferring an island array hard mask defined via electron-beam lithography into a continuous Co/Pd multilayer film using Ar sputter etching.…”

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confidence: 99%

Origin of magnetic switching field distribution in bit patterned media based on pre-patterned substrates

Pfau

Günther

Guehrs

et al. 2011

Applied Physics Letters

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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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Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

2010

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Intense interest in nanomagnetic materials is stimulated by the continuing quest for smaller, faster, and more energy efficient magnetic devices. [1,2] Rapid miniaturization has pushed the physical dimensions of magnetic devices into the submicrometer region, where new and intriguing size-dependent phenomena take effect. [3][4][5] At this length scale, the exchange and magnetostatic energies are of comparable magnitude and small variations of size or shape in the nanomagnetic system dramatically alters the energy levels and ground-state spin configuration. Moreover, to achieve specific functionality, especially with multicomponent devices, the overall magnetization process must be precisely engineered to ensure reliable operation. [6,7] Accordingly, the ability to effectively probe and analyze complex multilayer spin configurations and magnetization processes plays a key role in the development of next-generation magnetic nanotechnologies.[8]Here, we focus on a novel nanometric trilayer structure consisting of two shape-engineered permalloy (Py, Ni 80 Fe 20 ) layers separated by a nonmagnetic aluminum (Al) spacer, as a model experimental system. Using electron holography techniques, as described in the Experimental section, we directly characterize the magnetization reversal behavior of individual trilayer stacks and show that separate chirality-controlled vortex nucleation and annihilation events in the two magnetic layers are responsible for the underlying reversal mechanism. Accordingly, we exploit this reversal behavior to systematically obtain four distinct configurations of flux-closure, double-vortex states at remanence that are controllably generated by applying defined magnetic-field sequences to individual nanomagnetic trilayer stacks.The flux-closure state is attractive in device application to minimize undesired interaction between neighboring nanomagnets.[9] Specifically, the magnetic vortex state is characterized by a planar curling of the magnetic spin configuration with a specific chirality (either clockwise (CW) or counter-clockwise (CCW)) around a nanometer-sized vortex region, wherein the magnetization achieves an out-of-plane spin polarity.[10] The magnetic vortex state is acquired (through nucleation) in the ground-state remanent configuration, for nanomagnets within a certain range of aspect ratios for the characteristic planar dimension and thickness.[11] Here, we combine a semi-square and semi-disk planar shape to control the vortex chirality upon nucleation as illustrated by micromagnetic simulations for a single-layer structure (Fig.

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Microstructural origin of switching field distribution in patterned Co∕Pd multilayer nanodots

Abstract: Microstructure and magnetic properties of a Co/Pd multilayer on a controlled Pd/Si seed layer for double-layered perpendicular magnetic recording media

Cited by 75 publications

References 22 publications

Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

Influence of ion irradiation on switching field and switching field distribution in arrays of Co/Pd-based bit pattern media

Origin of magnetic switching field distribution in bit patterned media based on pre-patterned substrates

Control of Double‐Vortex Domain Configurations in a Shape‐Engineered Trilayer Nanomagnet System

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