Magnetic Properties of Two-Dimensional Ferromagnetic Semiconductors

Two-dimensional ferromagnetic semiconductors combine long-range magnetic order with a finite electronic band gap, offering a unique platform for low-dimensional spintronic devices and quantum technologies. In these van der Waals‐bonded sheets, magnetic ordering persists down to the monolayer limit despite thermal fluctuations that, in principle, would prevent spontaneous symmetry breaking. The interplay between reduced dimensionality and exchange interactions gives rise to pronounced magnetocrystalline anisotropy, enabling stability of ferromagnetic states at experimentally accessible temperatures. Key phenomena include thickness‐dependent Curie temperatures, strain‐tunable magnetic easy axes and hybridised spin‐lattice modes that shape magnon dispersion. Prototype materials such as chromium trihalides and chromium chalcogenides (for example CrSiTe₃, CrGeTe₃ and Cr₂Ge₂Te₆) exhibit a diversity of magnetic textures, from robust out‐of‐plane alignment to weak in‐plane anisotropy, governed by superexchange pathways through ligand orbitals. Comprehensive understanding of these properties underpins the design of heterostructures, strain‐engineered devices and novel sensors exploiting spin‐polarised transport and magneto‐optical effects.

Research from Nature Portfolio

Recent studies have elucidated how magneto‐elastic coupling drives structural modulations across the ferromagnetic transition in two‐dimensional CrGeTe₃. Thermal fluctuations induce an isostructural lattice contraction that enhances in‐plane magnetocrystalline anisotropy and shifts electronic bands, revealing a strong interplay between on‐site Coulomb interactions and spin‐orbit coupling. In parallel, neutron scattering measurements on monolayer analogue systems have uncovered anomalous in‐plane magnon damping and breakdown of quasiparticle conservation at zero temperature. These observations attest to dynamic spin–lattice coupling arising from quantum fluctuations, and demonstrate that in‐plane spin excitations form mixed spin–phonon quasiparticles distinct from conventional magnons.

Magnetic Properties of Two-Dimensional Ferromagnetic Semiconductors publication trend

The graph below shows the total number of articles in magnetic properties of two-dimensional ferromagnetic semiconductors across all publications each year (not limited to Nature Index journals).

Technical terms

Van der Waals materials: Layered solids in which adjacent sheets are bound by weak dispersion forces, enabling mechanical exfoliation to monolayers.

Ferromagnetism: Long-range alignment of magnetic moments in a material, resulting in a spontaneous net magnetisation below a characteristic temperature.

Curie temperature: The critical temperature above which a ferromagnet loses its spontaneous magnetisation and becomes paramagnetic.

Magnetocrystalline anisotropy: Dependence of magnetic energy on the orientation of magnetisation relative to the crystallographic axes.

Magnons: Quanta of collective spin‐wave excitations that propagate through an ordered magnetic lattice.

Spin–lattice coupling: Interaction between magnetic moments and atomic displacements, leading to hybridised quasiparticles and lattice distortions at magnetic transitions.

Superexchange: Indirect exchange interaction between magnetic ions mediated by non-magnetic ligands, governing the strength and sign of coupling in many insulators.

References

1. Abnormal thickness-dependent magneto-transport properties of vdW magnetic semiconductor Cr2Si2Te6. npj 2D Materials and Applications (2023).
2. Amorphous Ferromagnetic Metal in van der Waals Materials. Advanced Electronic Materials (2023).
3. Magnetic anisotropy of the van der Waals ferromagnet Cr2Ge2Te6 studied by angular-dependent x-ray magnetic circular dichroism. Physical Review Research (2022).
4. Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe3. Nature Communications (2022).
5. Magneto-strain effects in 2D ferromagnetic van der Waal material CrGeTe3. Scientific Reports (2023).