Novel multifunctional RKKY coupling layer for ultrathin perpendicular synthetic antiferromagnet

Chatterjee, Jyotirmoy; Auffret, S.; Sousa, R. C.; Coelho, Paulo; Prejbeanu, I. L.; Diény, B.

doi:10.1038/s41598-018-29913-6

Cited by 22 publications

(20 citation statements)

References 19 publications

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“…By taking B dep as a measure of the coupling magnitude, if the coupling were RKKY mediated, it should be on the order of a few Oersteds, corresponding to J ∼ 0.4×10 −3 erg/cm 2 (assuming an exchange field of H RKKY = 3 Oe, M s = 1100 emu/cm 3 , and t Ti = 2 nm). A RKKY effect of such a magnitude is about three orders of magnitude smaller than reported for the standard Co/Ru/Co multilayers [58]. Therefore, the origin of the asymmetry in the DW depinning and expansion is ascribed to a magnetostatic orange peel effect [scenario (i)], although minor contributions from the RKKY coupling cannot be excluded.…”

Section: Discussion Of the Different Coupling Scenariosmentioning

confidence: 92%

Asymmetric depinning of chiral domain walls in ferromagnetic trilayers

et al. 2020

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We show that the coupling between two ferromagnetic layers separated by a nonmagnetic spacer can be used to control the depinning of domain walls and induce unidirectional domain wall propagation. We investigated CoFeB/Ti/CoFeB trilayers where the easy axis of the magnetization of the top CoFeB layer is out-of-plane and that of the bottom layer is in-plane. Using Magneto-optic Kerr effect microscopy, we find that the depinning of a domain wall in the perpendicularly magnetized CoFeB layer is influenced by the orientation of the magnetization of the in-plane layer, which gives rise to a field-driven asymmetric domain expansion. This effect occurs due to the magnetic coupling between the internal magnetization of the domain wall and the magnetization of the in-plane CoFeB layer, which breaks the symmetry of updown and down-up homochiral Néel domain walls in the perpendicular CoFeB layer. Micromagnetic simulations support these findings by showing that the interlayer coupling either opposes or favors the Dzyaloshinskii-Moriya interaction in the domain wall, thereby generating an imbalance in the depinning fields. This effect also allows for artificially controlling the chirality and dynamics of domain walls in magnetic layers lacking a strong Dzyaloshinskii-Moriya interaction. I-INTRODUCTION The development of future magnetic memory and logic technologies requires efficient control of magnetization in nanometer-sized devices 1. In a ferromagnet (FM), information can be encoded in magnetic domains and manipulated by displacing them 2,3. A variety of device concepts based on domain wall (DW) motion has been proposed for memory and logic operations 4-6. Many of these proposals rely on unidirectional DW motion along a racetrack, which can be easily achieved by current-induced spin-torques 7-16 , rather than externally applied magnetic fields 3 .

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Section: Discussion Of the Different Coupling Scenariosmentioning

confidence: 92%

Asymmetric depinning of chiral domain walls in ferromagnetic trilayers

et al. 2020

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“…Moreover, a three‐step reversal process is observed due to larger RKKY exchange bias. [ 19 ] The magnetization of the CoGd (M s‐CoGd ) derived from the M(H) loop is 106 emu cm −3 . Therefore, the RKKY coupling energies (E ex = H ex M s‐CoGd t CoGd ) are calculated to be 0.123 and 0.01 erg cm −2 respectively for 2.5 and 3 nm Pt spacers.…”

Section: Resultsmentioning

confidence: 99%

RKKY Exchange Bias Mediated Ultrafast All‐Optical Switching of a Ferromagnet

Chatterjee

Polley

Pattabi

et al. 2021

Adv Funct Materials

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The discovery of ultrafast helicity‐independent all‐optical switching (HI‐AOS), as well as picosecond all‐electrical switching of a ferrimagnet, has inspired the ultrafast spintronics community to explore ultrafast switching of a ferromagnet to achieve practical ultrafast storage and memory devices. Two explored mechanisms of HI‐AOS of a ferromagnet in ferromagnet‐ferrimagnet heterostructure are: a) exploiting the indirect exchange coupling with and b) injection of non‐local spin current originated from a switching ferrimagnet. In this manuscript, exchange mediated HI‐AOS of a Ruderman–Kittel–Kasuya–Yosida (RKKY) exchange coupled “[Co/Pt]‐multilayers/Pt spacer/CoGd” heterostructure is demonstrated. The authors have measured layer‐resolved static magnetic properties, single‐shot HI‐AOS, and magnetization dynamics of the ferromagnetic Co/Pt multilayers (MLs), that are ferromagnetically or antiferromagnetically coupled with ferrimagnetic CoGd layers. Time‐resolved magnetization dynamics reveal a 3.5 ps switching time of the Co/Pt MLs, which is the fastest switching of a ferromagnet reported to date. Employing an extended microscopic three‐temperature model, the temporal dynamics of the exchange coupled ferromagnet–ferrimagnet heterostructure are simulated, qualitatively and quantitatively explaining the experimental switching phenomena. This work experimentally as well as theoretically establishes the mechanism of exchange mediated all‐optical switching of ferromagnet‐ferrimagnet heterostructures, which can be integrated with a magnetic tunnel junction for efficient reading after ultrafast energy‐efficient switching.

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“…We study the impact of the FL saturation field on GMR transfer curves, using superconducting quantum interference devicevibrating sample magnetometry (SQUID-VSM), polar magneto-optic Kerr effect (MOKE), and GMR measurement setups. The high H ex in the reference system and the FL saturation field control are achieved by using Co/Pt multilayer (ML) systems [22,[24][25][26][27], where PMA stems from strong spin-orbit coupling and d -d orbital hybridization at the interface [24,28,29]. The behavior in magnetization reversal and magnetoresistance are further investigated through micromagnetic simulations, focusing on switching fields and spin-canting effects [30,31] within the p-SAF reference system.…”

Section: Introductionmentioning

confidence: 99%

Spin-canting effects in GMR sensors with wide dynamic field range

Muehlenhoff¹,

Vogler²,

Raberg³

et al. 2020

Preprint

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Magnetoresistive (xMR) sensors find extensive application in science and industry, replacing Hall sensors in various low field environments. While there have been some efforts in increasing the dynamic field range of xMR sensors, Hall sensors remain to dominate high field applications due to their wide linear range. Using a perpendicular magnetized reference system and an in-plane free layer allows us to overcome this disadvantage of xMR sensors, and, furthermore, investigate spin-canting effects in interlayer exchange coupled perpendicular synthetic antiferromagnets (p-SAF). We created p-SAFs with exchange coupling fields of up to 10 kOe, based on magnetic Co/Pt multilayer systems. The p-SAFs are either designed as "single" p-SAFs, where two Co/Pt multilayers are interlayer exchange coupled via a 4 Å thick Ru spacer, or as "double" p-SAFs, where an additional Co layer is interlayer exchange coupled to the top multilayer. These p-SAFs are used for giant magnetoresistance (GMR) sensors with wide dynamic field range. By using a p-SAF as the reference system and employing an in-plane magnetic layer as the GMR's free layer, the linear range can be effectively increased limited only by the p-SAF's switching fields. Additionally, the magnetic anisotropy of the in-plane free layer is fully controlled, which allows saturation fields by design. With this, the entire spectrum from parallel to antiparallel alignment of free and reference layer is exploited, which yields the full GMR signal potential. Different configurations were investigated, ranging from free layer magnetic saturation at lower to far higher fields than the p-SAF's switching fields. We can show through micromagnetic simulations that certain GMR transfer curves are dominated by spin-canting effects in the interlayer exchange coupled reference system. Finally, our simulation results lay out the correlation of the p-SAF's design parameters and its magnetization reversal behavior.

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Novel multifunctional RKKY coupling layer for ultrathin perpendicular synthetic antiferromagnet

Cited by 22 publications

References 19 publications

Asymmetric depinning of chiral domain walls in ferromagnetic trilayers

Asymmetric depinning of chiral domain walls in ferromagnetic trilayers

RKKY Exchange Bias Mediated Ultrafast All‐Optical Switching of a Ferromagnet

Spin-canting effects in GMR sensors with wide dynamic field range

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