Strain-driven spin-Hall antiferromagnetic memory for 180° switching

Antiferromagnets exhibit ultrafast spin dynamics with response times in the picosecond range, produce negligible stray fields, and are promising to design high-density nonvolatile memories. NiO is an antiferromagnetic insulator whose Néel order can be switched by 90° using electric current in the spin-Hall system NiO/Pt [1], or piezoelectric strain in Ni/NiO/PMN-PT [2]. Although these switching schemes allow storage of information, the 90° state is thermally metastable.

We propose 180° reversal of the Néel order by leveraging both piezoelectric strain and spin-Hall effect in PMN-PT/NiO/Pt system. The reversal is accomplished by first realizing strain-induced perpendicular reorientation, followed by an electric current pulse that provides the antidamping torque necessary to tip the Néel order to the reversed easy-axis orientation. The antiferromagnetic state is read via exchange-bias-coupled magnetic tunnel junction. Modeling shows that the strain-driven NiO memory can switch under 100 ps, while consuming < 300 aJ/bit switching energy.

[1] Chen et al. Phys. Rev. Lett. 120, 207204 (2018).
[2] Zhang et al. Phys. Rev. B 95, 174420 (2017).