Chromium tribromide

CrBr₃

Also called chromium(III) bromide

van der Waals crystal magnet

The bromine sibling of CrI₃, and the more forgiving one. It stays a ferromagnet down to a single layer, which orders at 34 K, close to the 37 K of the bulk crystal, and, unlike in CrI₃, its layers align with each other in the bulk. Its spins point out of the plane, but with a much weaker preference than in CrI₃, which puts it closest of the chromium trihalides to an ideal Heisenberg magnet. In bilayers, the way the two sheets are stacked decides whether they align or oppose – the clearest demonstration that stacking sets the magnetic coupling between layers. Monolayers have even been measured in air.

Data sheet

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Kind of sheet: van der Waals crystal
Peels off a layered crystal, one sheet at a time
Behaves as: magnet
Band gap: Semiconducting: scanning tunnelling spectroscopy measures a gap of only 0.57 eV, far below the 1.68–2.1 eV long assumed from optical measurements, whose near-infrared light comes from a transition within the Cr³⁺ ions

In colour: this family, 0.57 eV. In grey: the other 41 families on the catalogue’s chart, each at the middle of its range. The dashed line marks bulk silicon, 1.12 eV.
Thickness: ~0.61 nm per layer
Structure: Cr³⁺ ions on a honeycomb lattice, each inside an octahedron of bromide ions – the same layer as CrI₃; unlike CrI₃ and CrCl₃, bulk crystals already take the rhombohedral BiI₃ stacking (R-3) at room temperature, and switch to the monoclinic stacking only above about 420 K
Space group: CrBr₃: bulk R3, monolayer P31m
Bulk: the Materials Project crystal linked below. Monolayer: the 2DMatPedia layer, as a periodic slab
Stability: Sensitive to air and moisture, though less than CrI₃: monolayers have been measured in air, but their edges degrade within about 15 minutes of exposure, so crystals are moved quickly to an inert atmosphere and thin flakes are encapsulated.
First made: 2019 – ferromagnetism in a monolayer, by magneto-photoluminescence (Zhang and colleagues) and by magneto-optics (Kim and colleagues); few-layer tunnel barriers a year earlier (Ghazaryan and colleagues)
Materials Project: CrBr₃
Computed crystal structure and properties
2DMatPedia: CrBr₃
Computed monolayer, exfoliated from a bulk crystal of the same compound

Compare with other materials

Key properties

Ferromagnetic down to a monolayer: a single layer orders at 34 K, seen by polarisation-resolved magneto-photoluminescence
Bulk crystals are ferromagnetic below 37 K, with their moments out of the plane
A much weaker anisotropy than CrI₃ – an anisotropy field of about 5 kOe in bulk – puts it closest of the three chromium trihalides to a Heisenberg magnet
In bilayers the stacking sets the coupling between layers: antiferromagnetic when both layers point the same way, ferromagnetic when one is turned relative to the other, as spin-polarised scanning tunnelling microscopy shows
Electrons tunnelling through barriers 2–6 layers thick lose energy mainly by emitting magnons at low temperature, a possible way to inject spins
Its near-infrared light comes from a transition within the Cr³⁺ ions, and its brightness changes markedly around the magnetic ordering temperature
Scanning tunnelling spectroscopy finds a gap of 0.57 eV, far smaller than the 1.68–2.1 eV long taken from optical measurements – which settles a long-running disagreement about its electronic structure
The halides mix: CrBr_xCl_3−x and CrBr_xI_3−x form across the whole composition range, with lattice parameters close to Vegard’s law, near-infrared photoluminescence that shifts with composition, and a change of stacking in the chloride–bromide series at x ≈ 1.8
Mixed with chloride, as CrCl_3−xBr_x, it hands over smoothly to CrCl₃: the easy axis turns from out of the plane into it, and the ordering temperature, optical gap and layer spacing all change linearly with the bromine content

How it is made

Bulk crystals from the elements: chromium and bromine react at 750 °C, then chemical vapour transport from 750 to 550 °C
Short chemical vapour transport straight onto yttria-stabilised zirconia, from 650 to 550 °C: sheets at most 25 nm thick in one step
Mixed-halide nanoplatelets a few nanometres high by the same route; the halide ratio barely shifts during transport, so the starting powder sets the composition
Molecular beam epitaxy of monolayers and bilayers on graphene or metal substrates
Mechanical exfoliation down to monolayers

Uses, and how close they are

Tunnel barriers that inject spins by emitting magnonslab
Model system for nearly isotropic (Heisenberg) magnetism and for coupling between layers set by stackinglab

Readiness runs lab → prototype → pilot → deployed.

Open problems

Which stackings form in thin flakes and bilayers, and can the coupling between layers be switched by changing the stacking?
What ordering in mixed-halide CrX₃ crystals produces the extra X-ray reflections that neither parent structure explains?

All 256 open problems on Flatland, by theme

Going deeper

Short notes for specialists. Choose a lens in the header and yours comes first.

For theoreticians · your lens

With only a weak out-of-plane anisotropy, CrBr₃ is the chromium trihalide closest to a Heisenberg magnet, and a monolayer still orders only because that small anisotropy keeps the Mermin–Wagner theorem from applying – a test of how little anisotropy two dimensions need. Tunnelling and magneto-optics on CrI₃, CrBr₃ and CrCl₃ are described by one nearest-neighbour spin model whose anisotropy changes systematically with the halogen. Coupling between layers depends on stacking, ferromagnetic or antiferromagnetic in bilayers, so any calculation has to fix the stacking first.

For experimentalists · your lens

Magneto-photoluminescence and magneto-optical Kerr measurements resolve the magnetisation of single layers; the monolayer orders at 34 K, and thicker flakes show hysteresis loops shaped by magnetic domains. In tunnel junctions, features in the tunnelling current mark the emission of magnons. Bilayers grown by molecular beam epitaxy let scanning tunnelling microscopy identify the stacking alongside the magnetic order.

For engineers · your lens

A Curie temperature below 40 K rules out room-temperature uses. CrBr₃ matters as the most forgiving chromium trihalide to handle, and as a tunnel barrier that filters and injects spins in low-temperature heterostructure experiments.

In the research tracks

Theory frontiers

Magnetic order in two dimensions

Recent news

The newest items tagged CrBr₃, from the news feed updated 22 Oct 2026.

Preprintnot yet peer reviewed 5 Oct 2026 arXiv

Adjoint-State Identifiability of Piezo-Tunable Valley Splitting in 2D Magnetic Heterostructures

Controlling valley degrees of freedom with mechanical strain is a promising approach for solid-state information processing. Current theoretical literature routinely predicts strain-tuned valley splitting at the microscopic level but rarely evaluates whether these quantum predictions remain statistically recoverable in…

TheoryCrBr₃ MoS₂

Preprintnot yet peer reviewed 5 Sep 2026 arXiv

Purely Electric-Field Control of Topological Magnetism in Two-Dimensional Magnets

Electrical control of topological magnetism is central to realizing energy-efficient topological spintronics. Yet most electric-field approaches modify the competing magnetic interactions through a nonselective rearrangement of low-energy electronic states, yielding coarse magnetic phase control that often requires…

TheoryCr₂Ge₂Te₆ Graphene CrBr₃

Preprintnot yet peer reviewed 10 May 2026 arXiv

Giant Rashba Splitting and Enhanced Nonlinear Berry-Phase Responses in Sliding-Tunable vdW MXene Heterostructures

Chalcogen-terminated van der Waals MXenes (M2CX2; M = Nb, Ta; X = S, Se) provide a robust platform for exploring strong spin-orbit coupling and proximity engineering. To probe their tunability and guide optimization of emergent properties, we systematically examine sister compounds and propose M2CS2/CrBr3…

TheoryExperimentMXenes CrBr₃

Preprintnot yet peer reviewed 17 Sep 2025 arXiv

Contrasting magnetic anisotropy in CrCl3 and CrBr3: A first-principles study

We present a first-principles study of the contrasting easy magnetization axes(EMAs) in the layered chromium trihalides CrCl3 and CrBr3, which exhibit in-plane and out-of-plane EMAs, respectively. Using density-functional theory calculations, we show that the EMA is determined by the interplay between spin-orbit…

TheoryCrBr₃ CrCl₃

All 4 items tagged CrBr₃ in the news feed · RSS feed for CrBr₃

Key references

Direct photoluminescence probing of ferromagnetism in monolayer two-dimensional CrBr₃Zhang et al. · Nano Letters 19, 3138 (2019)doi:10.1021/acs.nanolett.9b00553
Evolution of interlayer and intralayer magnetism in three atomically thin chromium trihalidesKim et al. · PNAS 116, 11131 (2019)doi:10.1073/pnas.1902100116
Direct observation of van der Waals stacking–dependent interlayer magnetismChen et al. · Science 366, 983 (2019)doi:10.1126/science.aav1937
Magnon-assisted tunnelling in van der Waals heterostructures based on CrBr₃Ghazaryan et al. · Nature Electronics 1, 344 (2018)doi:10.1038/s41928-018-0087-z
Small energy gap revealed in CrBr₃ by scanning tunneling spectroscopyBaral et al. · Physical Chemistry Chemical Physics 23, 3225 (2021)doi:10.1039/D0CP05633B
Crystal and magnetic structures in layered, transition metal dihalides and trihalidesMcGuire · Crystals 7, 121 (2017)cited by 478doi:10.3390/cryst7050121
Chromium trihalides CrX3 (X = Cl, Br, I): direct deposition of micro- and nanosheets on substrates by chemical vapor transportGrönke et al. · Advanced Materials Interfaces 6, 1901410 (2019)cited by 60doi:10.1002/admi.201901410
Controlled nanoplatelet deposition of 2D chromium trihalide solid solutionsFroeschke et al. · Chemistry of Materials 35, 4136 (2023)cited by 5doi:10.1021/acs.chemmater.2c03785
Controlling magnetic and optical properties of the van der Waals crystal CrCl₃−xBrx via mixed halide chemistryAbramchuk et al. · Advanced Materials 30, 1801325 (2018)doi:10.1002/adma.201801325
Synthesis, nanocrystal deposition and characterization of 2D transition metal trihalide solid solutionsFroeschke · Doctoral thesis, TU Dresden (2023)

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