Researchers have fabricated magnetic heterostructures down to single-digit nanometer dimensions by using individual carbon nanotubes as etching templates, according to research published in Nature Communications. The lithography-free strategy allows researchers to study exchange bias and electrical switching in sub-10 nm regimes.
Stabilizing magnetization in sub-10 nm ferromagnetic layers has presented a persistent obstacle for developing high-density spin-orbit torque magnetic random-access memory. While coupling ferromagnetic layers to antiferromagnetic materials provides exchange bias to stabilize nanoscale bits, conventional lithography methods struggle to verify the behavior at single-digit nanometer scales.
The research team applied the carbon nanotube patterning technique to perpendicularly magnetized stacks composed of platinum, cobalt, and iridium-manganese (Pt/Co/IrMn). Anomalous Hall effect measurements confirmed that exchange bias persisted below 10 nanometers, and electrical spin-orbit torque current successfully switched the structures.
Device scaling exposed distinct magnetic switching mechanisms between layers. Cobalt layers shifted from multi-domain reversal to abrupt single-domain reversal at reduced dimensions. Meanwhile, exchange bias switching maintained gradual behavior across all tested dimensions, reflecting collective antiferromagnetic moment reorientation driven by exchange-spring dynamics.
Hexin Li and Ke Zhang contributed equally as first authors to the study, which was supported by the National Natural Science Foundation of China and the National Key Research and Development Program of China. The research involved collaborators from Beihang University, Tsinghua University, and the Laboratoire Albert Fert in France.
