Interlayer Exchange Coupling in Magnetic Heterostructures

Interlayer exchange coupling (IEC) in magnetic heterostructures describes the indirect magnetic interaction between ferromagnetic layers separated by a non‐magnetic spacer. Predominantly mediated by oscillatory Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions, IEC alternates between ferromagnetic and antiferromagnetic alignment as spacer thickness and composition vary. The bilinear coupling term favours collinear spin arrangements, while higher‐order biquadratic contributions can stabilise noncollinear or canted states. Precision engineering of IEC underpins key spintronic devices, from magnetic tunnel junctions for nonvolatile memory to synthetic antiferromagnets as robust reference layers. Control knobs such as voltage gating, thermal modulation and spacer alloying enable dynamic tuning of both coupling magnitude and sign. Recent advances extend IEC applications to skyrmion racetrack memories and high-frequency spin-torque oscillators, addressing the demands of ultralow-power switching and millimetre-wave communications. As IEC integration scales to nanometre regimes, it remains central to the development of energy-efficient, high-performance magnetic technologies with global impact.

Research from Nature Portfolio

Recent studies have demonstrated stable antiferromagnetic IEC in Co68B32/Ir/Pt multilayers by varying Ir spacer thickness and repetition number, revealing a fivefold enhancement in skyrmion velocity alongside suppressed skyrmion Hall angles in optimised synthetic antiferromagnets. Concurrently, exploitation of bilinear and biquadratic couplings in spin-torque oscillators has achieved oscillation frequencies from 23 to 576 GHz and tunability exceeding 61 GHz per unit current density, introducing new routes for millimetre-wave frequency generation in next-generation communications.

Interlayer Exchange Coupling in Magnetic Heterostructures publication trend

The graph below shows the total number of articles in interlayer exchange coupling in magnetic heterostructures across all publications each year (not limited to Nature Index journals).

Technical terms

Interlayer exchange coupling (IEC): Indirect magnetic interaction between separate ferromagnetic layers mediated by conduction electrons or spacer magnetism.

Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction: An oscillatory exchange mechanism through conduction electrons that alternates coupling sign with spacer thickness.

Bilinear coupling: The first‐order IEC term promoting parallel or antiparallel spin alignment across layers.

Biquadratic coupling: A higher‐order IEC term that can stabilise noncollinear or canted spin configurations.

Synthetic antiferromagnet (SAF): A multilayer assembly engineered to exhibit antiferromagnetic alignment via IEC, often used as a reference layer.

Magnetic tunnel junction (MTJ): A device comprising two ferromagnetic electrodes separated by an insulating barrier, whose resistance depends on relative magnetisation orientation.

Spin-torque oscillator (STO): A nanoscale device that generates microwave or millimetre-wave signals via spin-transfer torque induced by electrical currents.

Skyrmion: A topologically stable, vortex-like spin texture that can propagate along nanotracks under low current densities.

References

1. Antiferromagnetic interlayer exchange coupled Co68B32/Ir/Pt multilayers. Scientific Reports (2024).
2. Voltage-controlled interlayer coupling in perpendicularly magnetized magnetic tunnel junctions. Nature Communications (2017).
3. Control of the noncollinear interlayer exchange coupling. Science Advances (2020).
4. Origin of noncollinear magnetization coupling across RuX layers. Physical Review B (2022).
5. Temperature Dependence of the Magnetic Properties of IrMn/CoFeB/Ru/CoFeB Exchange Biased Synthetic Antiferromagnets. Materials (2020).
6. Ultra-wide-band millimeter-wave generator using spin torque oscillator with strong interlayer exchange couplings. Scientific Reports (2022).
7. Controlled and deterministic creation of synthetic antiferromagnetic domains by focused ion beam irradiation. Applied Physics Letters (2021).