Tuning the interlayer exchange coupling between single perpendicularly magnetized CoFeB layers

Lavrijsen, Reinoud; Fernández-Pacheco, Amalio; Petit, D.; Mansell, Rhodri; Jh, Lee; Cowburn, R. P.

doi:10.1063/1.3682103

Cited by 54 publications

(42 citation statements)

References 21 publications

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“…24 The switch to full magnetization occurs abruptly at a field which can be controlled by tuning the interlayer exchange coupling between the CoFeB layers via the Pt layer thickness on either side of the Ru layer. 25 This effectively tunes the width of the low field antiparallel region; the higher the antiferromagnetic RKKY coupling, the higher the H SW . The SAF is also characterized by high out of plane anisotropy, and hence an easy axis of magnetization.…”

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Highly tunable perpendicularly magnetized synthetic antiferromagnets for biotechnology applications

Vemulkar

Mansell

Petit

et al. 2015

Applied Physics Letters

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Magnetic micro and nanoparticles are increasingly used in biotechnological applications due to the ability to control their behavior through an externally applied field. We demonstrate the fabrication of particles made from ultrathin perpendicularly magnetized CoFeB/Pt layers with antiferromagnetic interlayer coupling. The particles are characterized by zero moment at remanence, low susceptibility at low fields, and a large saturated moment created by the stacking of the basic coupled bilayer motif. We demonstrate the transfer of magnetic properties from thin films to lithographically defined 2 m particles which have been lifted off into solution. We simulate the minimum energy state of a synthetic antiferromagnetic bilayer system that is free to rotate in an applied field and show that the low field susceptibility of the system is equal to the magnetic hard axis followed by a sharp switch to full magnetization as the field is increased. This agrees with the experimental results and explains the behaviour of the particles in solution.

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Highly tunable perpendicularly magnetized synthetic antiferromagnets for biotechnology applications

Vemulkar

Mansell

Petit

et al. 2015

Applied Physics Letters

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“…Subsequently, the IEC was also demonstrated in the magnetic systems with perpendicular magnetic anisotropy (PMA), in which the magnetic orientations of magnetic layers lie normal to the film plane. 5 However, till date a very few studies have focused on the systems with adjacent magnetic layers having magnetization perpendicular to each other. Along these lines, we herein propose a system consisting of ordered-CoPt hard layer having strong PMA and a Ni-Fe soft layer with IMA for understanding the effects of IEC as a function of thickness of spacers such as Ru and Pt.…”

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Modifying exchange-spring behavior of CoPt/NiFe bilayer by inserting a Pt or Ru spacer

Hsu

Tsai

Lee

et al. 2015

Journal of Applied Physics

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We herein explore the possibility of obtaining tunable tilted magnetic anisotropy in ordered-CoPt (5 nm)/NiFe(tNiFe) bilayers through modifying their exchange spring behavior by inserting Pt and Ru-spacers. The tuning process of tilt angle magnetization of NiFe-layer was systematically investigated by varying the Pt or Ru thickness (tPt or tRu) from 0 to 8 nm at different thicknesses of NiFe (tNiFe = 1.5, 4.0, and 6.0 nm). Polar magneto-optic Kerr effect (p-MOKE) studies reveal that the bilayers grown in absence of spacers exhibit almost a rectangular hysteresis loop. With the insertion of Pt-spacer, the loop becomes more and more tilted as tPt increases; whereas, in the case of Ru-spacer, the nature of the loops is not simply changing in one direction. The estimated SQR⊥ (= θr/θs) values from the p-MOKE loops are found to monotonically decrease with increasing tPt when tPt ≦ 4 nm. In contrast, in the case of Ru-spacer, an oscillatory behavior for the SQR⊥ values is apparent when tRu ≦ 4 nm. As a result, an oscillatory tilted angle of NiFe spin configuration was obtained in the case of Ru-spacer; while a decoupling effect was prominent for the Pt-spacer. The results of present study reveal that the insertion of Pt and Ru-spacers as an appropriate means for realizing tunable tilted magnetic anisotropy in the CoPt/NiFe exchange springs.

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“…Another reason can be a well-developed layered structure with atomically flat interfaces of the present stacks, which was observed in high-resolution transmission electron microscopy experiments (results not shown). Recently, Choi et al 14 and Lavrijsen et al 15 reported that the ferromagnetic coupling observed in the very low t Ru range (t Ru < 0.6 nm) could be due to the roughness of the Ru spacer layer, possibly leading to the formation of ferromagnetic bridges.…”

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Interlayer exchange coupling between perpendicularly magnetized structures through a Ru/Ta composite spacer

Yun

Lim

Lee

2015

Applied Physics Letters

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In stacks using a Ru/Ta composite spacer [Pt/Co]6/Ru/Ta/CoFeB/MgO, both strong interlayer exchange coupling and perpendicular magnetic anisotropy are achieved. The composite spacer has the additional advantages of high post-annealing stability over a conventional Ru spacer; for a Ru (0.8 nm)/Ta (0.4 nm) spacer, where the antiparallel coupling is strongest, the coupling strength remains nearly constant at the highest annealing temperature of 375 °C. An interlayer exchange coupling is observed at very small Ru thicknesses down to 0.2 nm, which can be compared with the previous limit of 0.6 nm.

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Tuning the interlayer exchange coupling between single perpendicularly magnetized CoFeB layers

Cited by 54 publications

References 21 publications

Highly tunable perpendicularly magnetized synthetic antiferromagnets for biotechnology applications

Highly tunable perpendicularly magnetized synthetic antiferromagnets for biotechnology applications

Modifying exchange-spring behavior of CoPt/NiFe bilayer by inserting a Pt or Ru spacer

Interlayer exchange coupling between perpendicularly magnetized structures through a Ru/Ta composite spacer

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