Anisotropic Magnetoresistance Phenomena in Ferromagnetic Materials

Anisotropic magnetoresistance (AMR) describes the dependence of electrical resistance in a ferromagnetic conductor on the relative orientation of its magnetization and the direction of electric current. Originating from spin–orbit coupling, AMR arises when the probability of electron scattering varies with the angle between current flow and magnetic moments. Typically amounting to a few per cent change in resistivity, the effect has underpinned high‐precision magnetic sensors, position encoders and automotive applications for decades. Recent advances have revealed a nuanced interplay between intrinsic mechanisms—rooted in the electronic band structure—and extrinsic scattering by impurities or defects. The anisotropy can also adopt higher‐order symmetries in ordered alloys or epitaxial films and be tuned by crystal orientation, strain or interface engineering. Beyond its fundamental interest, AMR remains central to spintronic device design, where angular sensitivity and material microstructure dictate performance and energy efficiency.

Research from Nature Portfolio

Recent studies have quantified the temperature dependence of intrinsic and extrinsic AMR components using terahertz time‐domain spectroscopy on permalloy films. It was shown that the scattering‐independent intrinsic contribution remains nearly constant across a wide temperature range, whereas the extrinsic term, governed by impurity scattering, diminishes markedly upon warming. In a separate investigation, a negative spin Hall magnetoresistance was observed in normal metal/ferromagnet bilayers, revealing that interfacial spin–orbit coupling can reverse the conventional positive spin Hall signal. This finding highlights the importance of interface engineering for advanced spintronic architectures. Foundational work has also demonstrated a novel anomalous Hall magnetoresistance in ferromagnets, where spin accumulation and spin–charge conversion at sample surfaces generate an angular‐dependent resistivity with the same characteristic symmetry as spin Hall magnetoresistance, opening new avenues for charge–spin interconversion in a single ferromagnetic layer.

Anisotropic Magnetoresistance Phenomena in Ferromagnetic Materials publication trend

The graph below shows the total number of articles in anisotropic magnetoresistance phenomena in ferromagnetic materials across all publications each year (not limited to Nature Index journals).

Technical terms

Anisotropic magnetoresistance (AMR): Change in electrical resistance of a ferromagnet depending on the angle between current and magnetization.

Spin–orbit coupling (SOC): Interaction between an electron’s spin and its orbital motion around the atomic nucleus, central to magnetotransport effects.

Intrinsic contribution: Component of AMR arising from the material’s band structure and scattering‐independent electronic properties.

Extrinsic contribution: Component of AMR arising from spin‐dependent scattering of conduction electrons by impurities, defects or phonons.

Spin Hall magnetoresistance (SMR): Variation in resistance due to spin currents generated by the spin Hall effect interacting with an adjacent ferromagnet.

Relaxation time anisotropy: Directional variation in electron momentum relaxation rates that alters resistivity as the magnetization direction changes.

References

1. Temperature dependence of intrinsic and extrinsic contributions to anisotropic magnetoresistance. Scientific Reports (2021).
2. Negative spin Hall magnetoresistance of normal metal/ferromagnet bilayers. Nature Communications (2020).
3. Anomalous Hall magnetoresistance in a ferromagnet. Nature Communications (2018).
4. Broadband Terahertz Probes of Anisotropic Magnetoresistance Disentangle Extrinsic and Intrinsic Contributions. Physical Review X (2021).
5. Fourfold Anisotropic Magnetoresistance of L10 FePt Due to Relaxation Time Anisotropy. Physical Review Letters (2022).
6. Anisotropic magnetoresistance: materials, models and applications. Royal Society Open Science (2023).