Perpendicular Magnetic Anisotropy in Thin Film Multilayers

Perpendicular magnetic anisotropy (PMA) in thin film multilayers arises when the easy axis of magnetisation lies perpendicular to the film plane, a feature that is critical for high-density data storage and low-power spintronic devices. In ultrathin stacks of alternating ferromagnetic and non-magnetic layers, broken symmetry at interfaces and strong spin–orbit coupling generate interfacial anisotropy energies that can outweigh the shape anisotropy favouring in-plane magnetisation. Additional contributions from magnetoelastic coupling, induced either by lattice mismatch or by post-deposition annealing, can further enhance PMA in films with layer thicknesses well above the sub-nanometre scale. Materials such as Co/Pt, Co/Ni and Co/Pd multilayers have been extensively studied, with optimisation of composition, thickness ratio and seed-layer texture proving central to tuning anisotropy strength, thermal stability and switching fields. Advances in fabrication methods, including epitaxial growth and controlled interfacial engineering, now permit the robust integration of PMA films with ferroelectric substrates for voltage-controlled switching, and the realisation of domain-wall conduits for racetrack memories. The interplay of interfacial chemistry, strain and nanoscale morphology continues to define the global frontier in energy-efficient magnetisation control and device miniaturisation.

Research from Nature Portfolio

Recent studies have demonstrated that the incorporation of controlled surface and edge roughness in Pt/Co/AlOx trilayer microdisks on ferroelectric PMN-PT substrates enables strain-mediated tuning of coercivity and domain-wall depinning fields. By applying quasistatic electric fields, researchers have shown reversible reduction in switching fields and a broad coercivity distribution linked to interfacial oxygen content. Foundational work on Co/Ni multilayers deposited on PZT ferroelectric plates revealed that voltage-induced strain of less than 0.1% can reduce coercive fields by over 30%, as well as propagate domain walls through alternating tensile and compressive strains. This approach points to voltage-controlled, low-energy switching strategies for next-generation spintronic memory elements.

Perpendicular Magnetic Anisotropy in Thin Film Multilayers publication trend

The graph below shows the total number of articles in perpendicular magnetic anisotropy in thin film multilayers across all publications each year (not limited to Nature Index journals).

Technical terms

Perpendicular magnetic anisotropy (PMA): A magnetic state in which the preferred direction of magnetisation is normal to the plane of a thin film, governed by interfacial and spin–orbit effects.

Magnetoelastic coupling: Interaction between magnetic order and mechanical strain, whereby lattice distortions influence magnetic anisotropy and vice versa.

Coercivity: The applied magnetic field required to reduce the magnetisation of a ferromagnet to zero, indicative of switching energy and stability.

Domain wall depinning field: The threshold magnetic field necessary to overcome pinning sites and drive the motion of magnetic domain walls.

Ferromagnetic resonance (FMR): A spectroscopic technique that probes the dynamic response of magnetisation precession under microwave excitation, yielding anisotropy constants.

Spin-reorientation transition (SRT): A change in the easy axis of magnetisation driven by variations in temperature, thickness or competing anisotropy components.

References

1. Perpendicular magnetic anisotropy in multilayers arising from the interplay of thermal strains and diffusion-driven plastic deformation. Acta Materialia (2024).
2. Strain-assisted magnetization reversal in Co/Ni multilayers with perpendicular magnetic anisotropy. Scientific Reports (2016).
3. Interface Effects on Magnetic Anisotropy and Domain Wall Depinning Fields in Pt/Co/AlOx Thin Films. Magnetochemistry (2022).
4. Magnetic anisotropy in heterogeneous amorphous thin films: insights from thickness- and temperature-driven spin-reorientation. Journal of Physics D (2024).
5. Unlocking perpendicular magnetic anisotropy with Gd substitution in SmN. Applied Physics Letters (2023).