Electrical control of exchange bias in sub-10 nm regime enabled by single-nanotube patterning.

Abstract

Achieving stable magnetization in sub-10 nm ferromagnetic layers represents a fundamental bottleneck in spin-orbit torque magnetic random-access memory development. While exchange bias potentially offers stabilization at such scales through antiferromagnetic coupling, conventional lithography fundamentally limits nanoscale verification. Here, we introduce a lithography-free nanopatterning strategy exploiting individual carbon nanotubes as etching templates, enabling precise fabrication of exchange-biased heterostructures from tens of nanometers down to single-digit dimensions. In perpendicularly magnetized Pt/Co/IrMn stacks, we demonstrate robust exchange bias persistence even at sub-10 nm regimes and confirm effective spin-orbit torque switching through anomalous Hall effect measurements. Crucially, scaling reveals divergent switching mechanisms: Cobalt layers transition from multi-domain to abrupt single-domain reversal, while exchange bias switching maintains gradual characteristics consistent across sizes - indicating collective antiferromagnetic moment reorientation via exchange-spring dynamics. This work enables the physical patterning of sub-10 nm features for exchange bias stabilization, provides mechanistic insights into nanoscale magnetic switching, and establishes a viable pathway toward high-density spintronic memories.