Oral Session C1 (Thursday, February 15)
Chair: Shunsuke Fukami, Tohoku University

Keynote Talk
9: 00 - 9 : 40

Daniel C. Worledge
IBM ResearchSpin-transfer-torque MRAM: the next
revolution in memory
Spin-Transfer-Torque MRAM (STT-MRAM) was invented at IBM by John Slonczewski in theearly 1990s, using a spin-polarized current, instead of a magnetic field, to write a magnetic freelayer in a magnetic tunnel junction. The discovery of perpendicular magnetic anisotropy in thin
CoFeB/MgO layers at IBM and independently by Tohoku University enabled a dramaticreduction in the switching current, and opened the way to practical perpendicular magnetic tunnel
junctions for dense STT-MRAM.
This talk will provide an overview of STT-MRAM, including the two basic building blocks
described above. I’ll give an introduction to the physics of spin-transfer torque and applications ofSTT-MRAM. Then I will review why perpendicular magnetic anisotropy is advantageous for
STT-MRAM compared to in-plane anisotropy. I will discuss the research at IBM in 2009 that led
to our discovery of perpendicular anisotropy in thin CoFeB/MgO layers, and our use of theselayers to make the first practical perpendicular magnetic tunnel junctions and the first
demonstration of reliable writing in STT-MRAM [1]. Finally I will review our recent results on
methods to lower the switching current of STT-MRAM by using optimized magnetic materials
and double magnetic tunnel junctions, including our recent demonstration of reliable 250 ps
switching [2].
References[1] D. C. Worledge et al., "Switching distributions and write reliability of perpendicular spin torqueMRAM", 2010 International Electron Devices Meeting, pp. 12.5.1 (2010)[2] C. Safranski et al., “Reliable Sub-Nanosecond Switching in Magnetic Tunnel Junctions for MRAM
Applications”, IEEE Transactions on Electron Devices, 69, p7180 (2022)

Oral Session C1 (Thursday, February 15)
Chair: Shunsuke Fukami, Tohoku University

Keynote Talk
9: 40 - 10 : 20

Evgeny Y. Tsymbal
Department of Physics and Astronomy, University of Nebraska-Lincoln (UNL)

Antiferromagnetic tunnel junctions forspintronics
Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics, where an AFM Néel vector
is used as a state variable. Due to being robust against magnetic perturbations, producing no stray fields,
and exhibiting ultrafast dynamics, antiferromagnets can serve as promising functional materials for
spintronic applications. To realize this potential, eﬃcient electric control and detection of the AFM Néelvector are required. This keynote talk features fundamental properties of AFM tunnel junctions (AFMTJs)
as spintronic devices where such electric control and detection can be realized [1]. We emphasize criticalrequirements for observing a large tunneling magnetoresistance (TMR) eﬀect in AFMTJs with collinear[2] and noncollinear [3,4] AFM electrodes, such as crystallinity of the junction, AFM metals exhibiting
momentum-dependent spin polarization [2,3], and/or AFM metals supporting Néel spin currents [5]. We
further discuss the unique property of non-collinear antiferromagnets to sustain virtually 100% spinpolarization [4], the possibility of magnetic tunnel junctions (MTJs) with a single ferromagnetic electrode[6], and spin torques that are capable of Néel vector switching [5]. Overall, AFMTJs have potential to
become a new standard for spintronics providing larger magnetoresistive eﬀects, few orders of magnitude
faster switching speed, and much higher packing density than conventional MTJs.
References

1. Pal, B. et al. Josephson diode eﬀect from Cooper pair momentum in a topological semimetal. Nat. Phys. 18,
1228-1233 (2022).
2. Kim, J.-K. et al. Intrinsic supercurrent non-reciprocity coupled to the crystal structure of a van der Waals Josephsonbarrier. Nat. Commun. accepted (2024).
3. Sivakumar, P. K. et al. Long-range Phase Coherence and Second Order ɸ_0-Josephson Eﬀect in a DiracSemimetal 1T-PtTe2 submitted (2024).
4. Jeon, K.-R. et al. Zero-field polarity-reversible Josephson supercurrent diodes enabled by a proximity-magnetizedPt barrier. Nat. Mater. 21, 1008-1013 (2022).