Exchange coupled composite media for perpendicular magnetic recording

Victora, R. H.; Shen, Xiao

doi:10.1109/tmag.2005.855263

Cited by 180 publications

(88 citation statements)

References 7 publications

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“…5,6 As a result, modern magnetic materials possess increasing structural complexity enabling significant advances in functionalities, such as an increased energy product in permanent magnets, 7 improved magnetocaloric properties, 8 increasing areal storage density in magnetic recording media, and improved sensitivity and scalability of magnetic read heads. [9][10][11] The latter in particular are prototypical examples of complex magnetic multilayer structures. Here magnetoresistive properties are tailored through exchange coupling and exchange biasing in magnetic heterostructures.…”

Section: Introductionmentioning

confidence: 99%

Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling

Wang

Mukherjee

et al. 2011

Journal of Applied Physics

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Exchange coupled magnetic hard layer/soft layer thin films show a variety of complex magnetization reversal mechanisms depending on the hierarchy of interaction strengths within and between the films. Magnetization reversal can include uniform rotation, soft layer biasing, as well as exchange spring behavior. We investigate the magnetization reversal of a CoPt/Permalloy/Ta/Permalloy heterostructure. Here, Stoner-Wohlfarth-type uniform magnetization rotation of the virtually free Permalloy layer and exchange spring behavior of the strongly pinned Permalloy layer are found in the same sample. We investigate the complex magnetization reversal by polarized neutron reflectometry, magnetometry, and magneto-transport. The synergy of combining these experimental methods together with theoretical modeling is key to obtain the complete quantitative depth resolved information of the magnetization reversal processes for a multilayer of mesoscopic thickness.

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Section: Introductionmentioning

confidence: 99%

Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling

Wang

Mukherjee

et al. 2011

Journal of Applied Physics

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“…15 1 kA/ m=1 emu/ cm 3 . 16 Models which constrain the multipressure samples to have uniform magnetic depth profiles were examined and found to result in significantly worse fits to the data.…”

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confidence: 99%

“…[1][2][3][4][5] Such media use soft magnetic layers to decrease the necessary write field, and exchange couple those layers to hard magnetic layers that provide thermal stability. Recent calculations by Suess 6 proposed that a gradual transition from soft to hard anisotropy can result in additional gains in writeability while preserving thermal stability.…”

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confidence: 99%

Direct observation of magnetic gradient in Co/Pd pressure-graded media

Kirby

Watson²,

Davies³

et al. 2009

Journal of Applied Physics

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Magnetometry and neutron scattering have been used to study the magnetic properties of pressure graded Co/Pd multilayers. The grading of the multilayer structure was done by varying the deposition pressure during sputtering of the samples. Magnetic depth profiling by polarized neutron reflectometry directly shows that for pressure-graded samples, the magnetization changes significantly from one pressure region to the next, while control samples sputtered at uniform pressure exhibit essentially uniform magnetic depth profiles. Complementary magnetometry results suggest that the observed graded magnetic profiles are due in part to a decrease in saturation magnetization for regions deposited at progressively higher pressure. Increased deposition pressure is shown to increase coercivity, and for graded samples, the absence of discrete steps in the hysteresis loops implies exchange coupling among regions deposited at different pressures.

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“…The key physical phenomena are spin-orbit coupling effects (exchange coupling and magneto-crystalline anisotropy), structural complexity (lattice defects/strains), and thermal activation. Thermal effects and inter/intra exchange coupling have been studied experimentally and theoretically [1][2][3][4][5][6] but the behaviour of many systems cannot be explained by these effects alone. It was previously shown that the switching behavior of twophase perpendicular granular exchange coupled systems 4,7 can deviate from a coherent, Stoner-Wohlfarth type behaviour, 8 towards a Kondorsky-like model, 9 which is revealed through the angular dependence of remanent coercivity.…”

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confidence: 99%

“…One possible source of incoherency arises from an increased degree of lateral inter-granular exchange coupling, rather than from the intra-granular exchange spring. 5 An alternative explanation was deduced from experiments at elevated temperature, showing that a decrease in the depth of the StonerWohlfarth minimum can arise from thermal activation. 6 However, it has been demonstrated that a shift in the angle of applied field at which the minimum switching field occurs is caused by incoherent reversal induced by inter-granular exchange coupling or incoherency within larger grains, rather than thermal activation.…”

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confidence: 99%

Grain boundaries in granular materials—A fundamental limit for thermal stability

Saharan

Morrison

Ikeda

et al. 2013

Applied Physics Letters

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We show that thermal-stability and the associated switching field in well segregated, nanoscale granular materials is explained by grain boundary and interface effects. Grain boundaries pose a fundamental limit on scaling rooted in their chemical and morphological structure, while exchange interactions across interfaces cause the switching to deviate from the expected coherent Stoner-Wohlfarth behaviour. Measurements and simulations of CoCrPt-systems show a clear shift in applied field angle behaviour, arising from exchange-coupling between magnetic-phases, while the quantitative switching field can only be explained by a transition layer surrounding the grains. These results are potentially significant for Heat-Assisted-Magnetic Recording and Bit-Patterned-Media Recording.

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Exchange coupled composite media for perpendicular magnetic recording

Cited by 180 publications

References 7 publications

Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling

Magnetometry and transport data complement polarized neutron reflectometry in magnetic depth profiling

Direct observation of magnetic gradient in Co/Pd pressure-graded media

Grain boundaries in granular materials—A fundamental limit for thermal stability

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