Magnetic Anisotropy in Quantum Materials

Magnetic anisotropy—the directional dependence of a material’s magnetic properties—lies at the heart of contemporary research in quantum materials. Governed by spin–orbit coupling and crystal symmetry, anisotropy dictates the preferred orientation of magnetic moments and underpins the stability of spin configurations against thermal agitation. In two-dimensional magnets, single-atom magnets and interfacial heterostructures, the competition between magnetocrystalline, shape and interfacial anisotropies governs phenomena as diverse as perpendicular magnetisation, spin reorientation transitions and topological spin textures. Advances in first-principles modelling, atomically resolved spectroscopies and nanoscale fabrication have enabled systematic tuning of anisotropy energies at atomic and molecular scales. Realising large anisotropy energies at room temperature remains pivotal for high-density data storage, energy-efficient spintronics and emerging quantum-information devices.

Research from Nature Portfolio

Recent studies have elucidated strategies to amplify and control anisotropy in model quantum systems. The ultimate limit of bit miniaturisation was explored by adsorbing single transition-metal adatoms on defective two-dimensional layers, where vacancy-mediated orbital hybridisation and Jahn–Teller distortions were shown to switch the easy axis between in-plane and out-of-plane orientations and to yield enhanced anisotropy energies. At metal–metal interfaces, element-specific spectroscopies combined with ab initio calculations have revealed that anisotropic orbital moments in one layer can induce perpendicular magnetic anisotropy through proximity effects in the adjacent layer, highlighting the role of interfacial orbital engineering. In molecular nanostructures, attachment of small ligands to transition-metal dimers has been demonstrated to reorganise molecular orbitals, boosting magnetic anisotropy energies into the hundreds of millielectronvolts and pointing towards design rules for chemically engineered atomic magnets.

Magnetic Anisotropy in Quantum Materials publication trend

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

Technical terms

Magnetic anisotropy energy (MAE): The energy difference between magnetic configurations aligned along different crystallographic or structural directions.

Spin–orbit coupling: An interaction between an electron’s spin and its motion around the nucleus that gives rise to directional dependence of magnetic properties.

Magnetocrystalline anisotropy: Anisotropy originating from the crystal lattice symmetry and its coupling to electron orbitals.

Perpendicular magnetic anisotropy (PMA): A form of anisotropy in which the easy axis of magnetisation is normal to the film or layer plane.

First-principles calculation: A computational method based on fundamental quantum mechanics, without empirical parameters, to predict material properties.

Jahn–Teller distortion: A symmetry-lowering structural change in a molecule or crystal that removes degeneracies of electronic energy levels.

X-ray magnetic circular dichroism (XMCD): An element-specific spectroscopic technique that probes orbital and spin magnetic moments by measuring differences in absorption of circularly polarised x-rays.

References

1. Enhanced Magnetic Anisotropies of Single Transition-Metal Adatoms on a Defective MoS2 Monolayer. Scientific Reports (2015).
2. Anatomy of interfacial spin-orbit coupling in Co/Pd multilayers using X-ray magnetic circular dichroism and first-principles calculations. Scientific Reports (2018).
3. Large magnetic anisotropy in chemically engineered iridium dimer. Communications Physics (2018).
4. Understanding magnetocrystalline anisotropy based on orbital and quadrupole moments. Journal of Physics Condensed Matter (2022).
5. Validity of perturbative methods to treat the spin–orbit interaction: application to magnetocrystalline anisotropy. New Journal of Physics (2019).
6. Chemically Engineering Magnetic Anisotropy of 2D Metalloporphyrin. Advanced Science (2017).