The setting of spin textures in antiferromagnets (AFMs) provides a potential route to antiferromagnetic spintronic devices with non-collinear spin states such as skyrmions, bubbles and domain walls. In this work, a consortium of physicists from SPINTEC and York establish a solution for overcoming the challenge of nucleating localized real-space spin textures in AFMs, promoting the extension of local spin texture studies beyond ferromagnets (FMs).
A skyrmion in the Pt/Co/NiFe ferromagnet is used as a template for the setting of the underlying IrMn antiferromagnet, using a thermal cycling procedure.
The physics of AFMs is very rich, sometimes unique and unexpected compared to their FMs counterparts.
A particular topological state of interest would be antiferromagnetic skyrmions (AFM Sks). Due to the anti-parallel interatomic exchange interactions they have not only zero net magnetization but also zero topological charge, which ensure robustness against external fields and vanishing Sk Hall effects, and a subsequent straight trajectory. Other predicted effects of AFM Sks on the transport properties include the non-vanishing topological spin Hall effect and a longitudinal Sk velocity exceeding that of the FM Sks. These properties make AFM Sks not only fascinating subjects for studies on topology but also competitive information carrier candidates for ultra-dense, ultrafast, low-power spintronic devices.
Controlling the magnetic order of AFMs is challenging due to their vanishing net magnetization. For this reason, the study of local spin textures in AFMs is restricted by the difficulty in nucleating such states.
Here, we use atomistic simulations to demonstrate a local nucleation of spin textures in AFM grains that does not require complex device geometries and is applicable beyond metallic AFMs. Utilizing the exchange bias coupling at a FM/AFM interface and a thermal cycling procedure, we set the spin texture in the AFM grains during their magnetic ordering from predefined spin textures in the FM. This method follows previous experimental works on setting AFM domains and domain walls, vortices, and bubbles. We nucleate Sks in a continuous thin film FM using a carefully optimized magnetic stack of //Pt/Co/NiFe and an external field. We then use this as a template for the setting of the underlying AFM grains of the IrMn// material. This setting was shown to extend beyond the interface through the entire thickness of the AFM (here 5nm). The set AFM textures showed remarkable stability against field perturbations and the setting efficiency as well as the morphologies of the set AFM textures were shown to depend on various material parameters. Using consecutive thermal and field cycling processes made it possible to isolate the AFM spin texture, opening up perspectives for further studies of spintronic properties of isolated, localised spin textures in an AFM.
Team: ANTIFERROMAGNETIC SPINTRONICS, THEORY/SIMULATION
Collaboration: University of York (UK)
Funding: PHC 46298XC; EPSRC EP/V007211/1
Further reading: Local setting of spin textures in a granular antiferromagnet, , M. Leiviskä✉, S. Jenkins, R. F. L. Evans✉, D. Gusakova, V. Baltz✉, Phys. Rev. B 108, 184424 (2023).
https://doi.org/10.1103/PhysRevB.108.184424/ Open access: hal-04008443
Contact at SPINTEC: Vincent BALTZ