Van der Waals Antiferromagnets: From Early Discoveries to Future Directions in the 2D Limit

Abstract

The emergence of a long-range magnetic order in the atomically thin, two-dimensional (2D) limit has long remained a fundamental question in condensed matter physics. The advent of exfoliable van der Waals (vdW) materials, particularly transition-metal phosphorus trisulfides (T MPS3; T M = Fe, Ni, and Mn), provided the first experimental access to this regime and established a foundational platform for investigating 2D magnetism. The 2016 experimental demonstrations of intrinsic magnetism in monolayer FePS3 provided a platform to test key aspects of 2D Ising criticality in the true 2D limit. It was followed by a rapid growth resulting in a wealth of emergent phenomena arising from the interplay of low-dimensional magnetism and quantum materials. We begin this review with the historical development of vdW antiferromagnets and highlight the key physical insights gained over the past decade. We finish with emerging opportunities in which vdW antiferromagnets can serve as versatile platforms for exploring low-dimensional magnetism and its interplay with other quantum degrees of freedom.

Figures (8)

• Figure 1: Conceptual landscape of 2D magnets within the three-dimensional space of spatial dimensionality, lattice geometry and spin symmetry.
• Figure 2: Chronological development of van der Waals magnetic material platforms (2016--2023). The timeline traces major experimental discoveries and their characterization, beginning with the first two-dimensional magnets (FePS$_3$, MnPS$_3$, NiPS$_3$) in 2016, followed by the first ferromagnetic systems (Cr$_2$Ge$_2$Te$_6$, CrI$_3$) in 2017, and progressing through successive breakthroughs including high-temperature ferromagnets (Fe$_3$GeTe$_2$, 2018), topological and air-stable antiferromagnets (MnBi$_2$Te$_4$, CrSBr, 2020--2021), multiferroic and air-stable systems (NiI$_2$, CrPS$_4$, 2021), twist-tunable magnets (2021--2022), and topological magnets (Co$_{1/3}$TaS$_2$, 2023).
• Figure 3: Crystal field splitting of 3$d$ orbitals and resulting spin anisotropy in transition metal phosphorous trichalcogenides. Top row: Octahedral crystal field splitting ($e_g$ and $t_{2g}$ orbitals) for FePS$_3$, NiPS$_3$, and MnPS$_3$. Middle row: Trigonal elongation or compression of the octahedral environment, leading to further splitting of the $d$-orbitals into $e'_g$ and $a_{1g}$ states. The blue vertical arrows qualitatively illustrate the splitting. Bottom row: Resulting magnetic anisotropy and spin models. The bottom row illustrations are adapted from wang2022magnetic, Copyright © 2022 The Authors.
• Figure 4: Temperature-dependent Raman spectroscopy and magnetic characterization of bulk FePS$_3$. (a) The temperature dependence of the Raman spectrum from 10 K to 295 K reveals six phonon modes; low-frequency modes P$_1$ and P$_2$ (iron vibrations) exhibit pronounced intensity changes across the magnetic transition, whereas higher-energy modes remain relatively stable. (b) Magnetic susceptibility measured along the $ab$-plane (black spheres) and $c$-axis (gray spheres) exhibits a sharp transition at $T_N \approx 118$ K, with the inset showing zig-zag antiferromagnetic alignment of Fe moments. (c) Low-frequency Raman modes (P$_{1a}$ and P$_2$) exhibit dramatic intensity increase below $T_N$. In contrast, higher-energy modes remain temperature-independent, confirming that magnetic ordering induces Brillouin zone folding and couples magnetic and vibrational excitations. The figure is adapted from lee2016ising.
• Figure 5: (a) Atomic force microscopy (AFM) image of exfoliated CrCl$_3$ flakes on silicon substrate with numbered profiles (1, 2, 3) indicating regions of quantitative analysis. (b) Corresponding magnetic force microscopy (MFM) image acquired at 50 kOe and 14 K, revealing clear magnetic contrast that correlates with flake thickness; dotted lines denote the same profiles as in (a) for direct comparison. (c) Sequence of MFM images acquired at 14 K under progressively decreasing magnetic fields (30 kOe, 10 kOe, 5 kOe, 2.5 kOe, 1 kOe, and demagnetized state), demonstrating field-dependent magnetization reversal. (d) Normalized X-ray photoemission electron microscopy (X-PEEM) image of a 48 nm thick NiPS$_3$ flake recorded at 70 K with photon energy 850.2 eV; the upper inset shows the X-ray incidence direction and electric field polarization geometry, while the lower inset displays the corresponding optical microscope image. (e) X-ray magnetic linear dichroism (XMLD) asymmetry map of the same region, revealing the spatial distribution of magnetic anisotropy and spin orientation. (f) Stray magnetic field ($B_S$) image mapping the nanoscale spin texture; the top and bottom five-layer regions exhibit opposite magnetization states ($|+5\rangle$ and $|-5\rangle$), while the intervening even-layer region displays a weak field signature indicative of antiphase domain walls between $|+6\rangle = \uparrow\downarrow\uparrow\downarrow\uparrow\downarrow$ and $|-6\rangle = \downarrow\uparrow\downarrow\uparrow\downarrow\uparrow$ configurations. Panel (a)-(c) are adapted from serri2020enhancement, Copyright © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, panels (d) and (e) are from lee2024imaging, and panel (f) is from wang2025configurable, Copyright © 2025 Nature publications.