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SUMMARY:2026 Scott Lectures: 2D van der Waals materials for spintronics - 
 Prof Stuart Parkin (Max Planck Institute of Microstructure Physics)
DTSTART:20260225T161500Z
DTEND:20260225T171500Z
UID:TALK245044@talks.cam.ac.uk
CONTACT:Vanessa Bismuth
DESCRIPTION:The family of 2D van der Waals (vdw) materials shows a wide ra
 nge of highly interesting properties. We discuss these materials in the co
 ntext of spintronic phenomena and potential devices. In particular\, vdw l
 ayers allow for novel ultrathin tunnel barriers for magnetic tunnel juncti
 ons (MTJs). \n\nMagnetic tunnel junctions are used today as magnetic field
  sensors in magnetic disk drives that store 70% of all digital data today.
  MTJs are also the basis of high performance\, non-volatile magnetic rando
 m access memories\, that is a memory technology available from the major s
 emiconductor foundries today. Such MTJs are formed from complex multilayer
 s formed from ultrathin ferromagnetic layers each of which generates stray
  magnetic fields that results in coupling within and between MTJs. \n\nTod
 ay’s MTJs use synthetic antiferromagnetic sandwiches that eliminate thes
 e stray fields. We have demonstrated an all-antiferromagnetic tunnel junct
 ion that is formed from two bilayers of the insulating van der Waals antif
 erromagnet CrSBr that are twisted at a non-zero angle. These junctions exh
 ibit two (or more) non-volatile states in zero magnetic field with very la
 rge tunneling magnetoresistance values (TMR)Nexceeding 1\,000 %1. We discu
 ss the origin of these giant TMR values and show how the magnitude depends
  on the twist angle. These high TMR values depend on the structural perfec
 tion of the vdw layers that is very difficult to achieve in conventional t
 unnel barriers formed from insulating oxides or nitrides. We show that the
  perfection of vdw ferromagnetic metallic layers allows for very high curr
 ent induced domain wall mobilities in racetracks formed from such vdw mate
 rials. These mobilities are even higher than those found in state of the a
 rt racetrack memory devices2. On the other hand\, we find structural defec
 ts in many vdw materials that appear to be intrinsic to such materials. Fo
 r example\, we find Fe vacancies in specific Wyckoff sites within the vdw 
 layers in the ferromagnetic Fe3GeTe2. These result\, in a non-centrosymmet
 ric crystal structure that\, thereby\, allows for the presence of Neel-lik
 e skyrmions3. Perhaps\, even more interestingly the presence of Fe atoms r
 andomly distributed within the vdw gaps in Fe3GeTe2 behave as the first 2D
  spin glass4. \n\n* Funded by European Research Council Advanced Grant “
 SUPERMINT” (2022-2027).\n\n1: Chen\, Y. et al. Twist-assisted all-antife
 rromagnetic tunnel junction in the atomic limit. Nature 632\, 1045–1051 
 (2024). \n2: Yang\, S.-H.\, Ryu\, K.-S. & Parkin\, S. S. P. Domain-wall ve
 locities of up to 750 ms−1 driven by exchange-coupling torque in synthet
 ic antiferromagnets. Nat. Nanotechnol. 10\, 221–226 (2015). https://doi.
 org/10.1038/nnano.2014.324\n3: Chakraborty\, A. et al. Magnetic skyrmions 
 in a thickness tunable 2D ferromagnet from a defect driven Dzyaloshinskii-
 Moriya interaction. Adv. Mater. 34\, 2108637 (2022). https://doi.org/10.10
 02/adma.202108637\n4: Pal\, B. et al. Realization of a Spin Glass in a two
 -dimensional van der Waals material. Science (accepted) (2025). 
LOCATION:Ray Dolby Auditorium\, Ray Dolby Centre\, Cavendish Laboratory\, 
 JJ Thomson Avenue\, CB3 0US
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