Field-free magnetization reversal by spin-Hall effect and exchange bias

Abstract

As the first magnetic random access memories are finding their way onto the market, an important issue remains to be solved: the current density required to write magnetic bits becomes prohibitively high as bit dimensions are reduced. Recently, spin–orbit torques and the spin-Hall effect in particular have attracted significant interest, as they enable magnetization reversal without high current densities running through the tunnel barrier. For perpendicularly magnetized layers, however, the technological implementation of the spin-Hall effect is hampered by the necessity of an in-plane magnetic field for deterministic switching. Here we interface a thin ferromagnetic layer with an anti-ferromagnetic material. An in-plane exchange bias is created and shown to enable field-free S HE-driven magnetization reversal of a perpendicularly magnetized Pt/Co/IrMn structure. Aside from the potential technological implications, our experiment provides additional insight into the local spin structure at the ferromagnetic/anti-ferromagnetic interface.

Joule Heating Effect on Field-Free Magnetization Switching by Spin-Orbit Torque in Exchange-Biased Systems

“…Field-free switching has been achieved by introducing a lateral structural asymmetry, where the thickness of one layer is changed laterally [10,19,20] or by inducing a tilt in the uniaxial anisotropy axis [21]. More recently, field-free switching was realized in the antiferromagnet and ferromagnet systems, where some form of in-plane exchange bias (EB) is used instead of an external field [22][23][24][25].…”

Dzyaloshinskii-Moriya Interaction across an Antiferromagnet-Ferromagnet Interface

“…The DMI strength is enhanced by a factor of 7 with increasing IrMn layer thickness in the range of 1-7.5 nm. Our findings provide deeper insight into the coupling at AFM/FM interface and may stimulate new device concepts utilizing chiral spin textures such as magnetic skyrmions in AFM/FM heterostructures.Control of spins in ferromagnets (FMs) utilizing antiferromagnets (AFMs) is an emerging branch of spintronics [1][2][3][4][5] . By placing an AFM layer adjacent to the FM layer, the unique electric, magnetic and transport properties of the AFM may be used to control the FM layer via interfacial coupling.…”

“…Control of spins in ferromagnets (FMs) utilizing antiferromagnets (AFMs) is an emerging branch of spintronics [1][2][3][4][5] . By placing an AFM layer adjacent to the FM layer, the unique electric, magnetic and transport properties of the AFM may be used to control the FM layer via interfacial coupling.…”

“…For instance, electric current-induced magnetization switching of FM without an external magnetic field has been realized in the AFM/FM systems [1][2][3][4] . These pioneering experiments have been shown to generate the pure spin current in the AFM or at the AFM/FM interface 1,2,[14][15][16] and to utilize the exchange bias to break the switching symmetry [1][2][3][4] . Moreover, coherent spin precession in the FM layer can be effectively excited by an ultrafast spin-exchange-coupling torque across the AFM/FM interface 5 .…”

Influence of heavy metal materials on magnetic properties of Pt/Co/heavy metal tri-layered structures

“…These features could enable a leading class of memory and logic devices. [1][2][3] Pt in contact with Co is well known to generate an interfacial perpendicular magnetic anisotropy (PMA) with a (111) texture, [4][5][6][7][8][9] and the Pt/Co/heavy metal (HM) trilayered structures are under intense investigation to explore a number of emerging spin-related effects, such as spinorbit torque (SOT), [10][11][12][13][14] domain wall motion, 15,16 and room temperature skyrmions. [17][18][19] For instance, Co/Pt-based multilayers with large PMA were applied as bottom pinned layers in perpendicular magnetic tunnel junctions.…”