Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

Zha, Chaolin; Dumas, Randy K.; Fang, Yeyu; Bonanni, Valentina; Nogués, J.; Åkerman, Johan

doi:10.1063/1.3505521

Cited by 52 publications

(34 citation statements)

References 30 publications

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“…The peak is located at a more negative H R value because the higher annealing temperature has increased the overall L1 0 ordering leading to an increase in anisotropy. As previously observed, 15 the increased annealing temperature leads to significant interdiffusion, which results in a compositionally homogenous film with little to no anisotropy gradient and therefore nearly identical behavior in the AGM and MOKE measurements.…”

supporting

confidence: 76%

“…15 In conjunction with the fabrication, the subsequent analysis of graded materials is not trivial and often requires complicated measurement apparatuses. For example, the inherent depth sensitivity of polarized neutron reflectivity measurements has recently been used to directly probe the anisotropy gradient of multilayered Co/Pd samples.…”

mentioning

confidence: 99%

“…[10][11][12][13][14] However, the realization of a continuous anisotropy gradient was recently achieved in properly annealed compositionally graded thin FePtCu films. 15 In conjunction with the fabrication, the subsequent analysis of graded materials is not trivial and often requires complicated measurement apparatuses. For example, the inherent depth sensitivity of polarized neutron reflectivity measurements has recently been used to directly probe the anisotropy gradient of multilayered Co/Pd samples.…”

mentioning

confidence: 99%

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First-order reversal curve analysis of graded anisotropy FePtCu films

Bonanni

Fang

Dumas

et al. 2010

Applied Physics Letters

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The reversal mechanisms of graded anisotropy FePtCu films have been investigated by alternating gradient magnetometer ͑AGM͒ and magneto-optical Kerr effect ͑MOKE͒ measurements with first-order reversal curve ͑FORC͒ techniques. The AGM-FORC analysis, which clearly shows the presence of soft and hard components, is unable to resolve how these phases are distributed throughout the film thickness. MOKE-FORC measurements, which preferentially probe the surface of the film, reveal that the soft components are indeed located toward the top surface. Combining AGM-FORC with the inherent surface sensitivity of MOKE-FORC analysis allows for a comprehensive analysis of heterogeneous systems such as graded materials. © 2010 American Institute of Physics. ͓doi:10.1063/1.3515907͔Graded anisotropy materials 1,2 have joined the ranks of tilted 3,4 and exchange coupled composite 5 ͑ECC͒ recording media as possible solutions to the magnetic recording trilemma, 6,7 where simultaneously balancing the thermal stability and signal-to-noise ratio with the writability of a given bit is necessary. Energy-assisted recording techniques, such as heat-assisted magnetic recording 8 and microwave-assisted magnetic recording, 9 rely on adding energy to the media in order to temporarily surmount the switching barrier with modest applied fields. In graded materials, which are predicted to provide additional gains in writability over conventional bilayer hard/soft ECC media, the anisotropy is systematically varied such that the switching field is reduced by the low anisotropy layers, while the high anisotropy layers preserve thermal stability. There have been few reports, mostly based on rather thick multilayered structures, on the successful creation of graded materials.10-14 However, the realization of a continuous anisotropy gradient was recently achieved in properly annealed compositionally graded thin FePtCu films. 15 In conjunction with the fabrication, the subsequent analysis of graded materials is not trivial and often requires complicated measurement apparatuses. For example, the inherent depth sensitivity of polarized neutron reflectivity measurements has recently been used to directly probe the anisotropy gradient of multilayered Co/Pd samples. 12,13 In this letter, we report on a relatively simple measurement and analysis technique that combines first-order reversal curve ͑FORC͒ 16-22 measurements with the inherent surface sensitivity of the magneto-optical Kerr effect ͑MOKE͒ to analyze FePtCu films with a continuously graded anisotropy. In addition to providing a useful qualitative fingerprint of the magnetization reversal mechanisms, the FORC techniques are able to extract a wealth of quantitative information not readily accessible from standard major loop or remanence curve analysis. For example, information on distributions of key magnetic parameters, interactions, and phase identification in a variety of bulk, thin film, and patterned systems has been shown. [16][17][18][19][20][21][22] To date, however, FORC analysis has focused ...

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confidence: 99%

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confidence: 99%

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First-order reversal curve analysis of graded anisotropy FePtCu films

Bonanni

Fang

Dumas

et al. 2010

Applied Physics Letters

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“…One possible way to circumvent this problem may be to use materials with lower K u (i.e., soft) and tune their effective anisotropy by coupling them to high K u (i.e., hard) [143] or by using antiferromagnets [399]. An alternative approach would be to reduce the effective anisotropy of high K u (i.e., hard) nanoparticles by coupling them with low K u (i.e., soft) materials, for example in a core/shell structure, similarly to what has been proposed for continuous thin film media [386,389,390]. In these cases, the soft counterpart acts to reduce the switching field (allowing the write-head to write the information) while the hard part preserves thermal stability.…”

Section: Recording Mediamentioning

confidence: 99%

“…Thus, to have viable recording media the thermal stability and SNR must be simultaneously balanced with the writtability of a given bit. To overcome this hurdle new types of recording media have been proposed such as exchange coupled composites [386], tilted anisotropy [387,388] and gradient anisotropy [389,390]. Nevertheless, these approaches also have their limits for sufficiently high densities.…”

Section: Recording Mediamentioning

confidence: 99%

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

et al. 2015

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A B S T R A C TThe applications of exchange coupled bi-magnetic hard/soft and soft/hard ferromagnetic core/shell nanoparticles are reviewed. After a brief description of the main synthesis approaches and the core/shell structural-morphological characterization, the basic static and dynamic magnetic properties are presented. Five different types of prospective applications, based on diverse patents and research articles, are described: permanent magnets, recording media, microwave absorption, biomedical applications and other applications. Both the advantages of the core/shell morphology and some of the remaining challenges are discussed.

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2.3.2 FePt-based nanomaterials

Djéga‐Mariadassou

2015

Nanocrystalline Materials, Part B

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Continuously graded anisotropy in single (Fe53Pt47)100−xCux films

Cited by 52 publications

References 30 publications

First-order reversal curve analysis of graded anisotropy FePtCu films

First-order reversal curve analysis of graded anisotropy FePtCu films

Applications of exchange coupled bi-magnetic hard/soft and soft/hard magnetic core/shell nanoparticles

2.3.2 FePt-based nanomaterials

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