Spin-transition modulated light-emitting devices in a 2D magnet

Domain: neuroscience
Published: 2026-04-08
Editorial outcome: major_revision

Abstract
Emerging two-dimensional magnetic semiconductors represent transformative platforms to
explore magneto-optics and opto-spintronic applications. Though two-dimensional opto-
spintronics has attracted tremendous research efforts in spin-dependent photodetectors and non-
volatile memory components, the realization of one core application - spin-modulated light-
emitting device - remains elusive so far. Here we successfully realize prototype spin-modulated
light-emitting device integrated with a two-dimensional semiconducting magnet chromium sulfide
bromide, demonstrating considerable electroluminescence down to bilayers. Intriguingly, its
discovered to be directly manipulated by spin-flip and spin-canting transitions. Notably, the
intrinsic carrier-tunable interlayer magnetic coupling in chromium sulfide bromide enables
electroluminescence to actively amplify magnetic hysteresis (via spin-flip) and continuously tune
magnetic order (via spin-canting) with robust anisotropy, establishing a connection between carrier
injection, magnetic phase transitions, and optical emission. The prototype demonstration of spin-
modulated light-emitting device establishes an indispensable scheme of opto-spintronic devices
leveraging two-dimensional spin transitions and strong excitonic effects, presenting a critical step
towards integrated two-dimensional opto-spintronics.

Introduction
Opto-spintronics, merging photonic, electronic, and magnetic functionalities, becomes a
novel but desirable paradigm for future information technologies1-4. Compared with conventional
charge-based electronics, this paradigm exploits electron spins as the fundamental variable for
information processing and storage, promising new functionalities with significantly reduced
energy consumption. For instance, non-volatile memory devices feature optical writing and
electrical readout of the spin orders5,6, and neuromorphic computing hardware employ spin-based
artificial synapses7. By leveraging spin-wave excitations, opto-magnonic circuits and quantum
transduction platforms have also been proposed and developed8. As one of the fundamental
optoelectronic components, light-emitting devices (LEDs) advance to unexplored versatility when
their electrical injections involve profound spin manipulations9-12. A critical bottleneck in opto-
spintronics is cryogenic operation (<10 K) of spin-dependent effects, far from practical room-
temperature requirements. This stems from the thermal fragility of two-dimensional (2D) magnetic
order and enhanced non-radiative recombination in 2D semiconductors.

The emerging vdW magnets have been recently extensively studied for striking fundamental
physical breakthroughs with unconventional 2D magnetism13,14. The confluence of inherent 2D
magnetism, electronic structures, and weak dielectric screening in the layered structures suggests
unprecedented functionalities to opto-spintronic components9. For example, spin-dependent
photodetectors15-17, spin-photovoltaics18 with magnetic CrI and MnSe have been proposed;
3
Moreover, non-volatile memory component with magnetic four-layer CrI and VSe has also been
3 2
designed19. However, as one core application of 2D opto-spintronics, no LED with spin-based
functionality has been realized so far20-23. Here, we report the realization of a prototype spin-
modulated LED (spin-LED) in CrSBr-based quantum well (QW) structures, achieving
considerable electroluminescence (EL) down to bilayer CrSBr. Unlike EL in conventional
semiconductors dictated by band structure and carrier recombinations24-27, the spin-exciton
coupling in CrSBr introduces versatile manipulations of its EL. Remarkably, the EL can be fully
manipulated with pronounced magnetic hysteresis by spin-flip transitions; Meanwhile, the EL can
be modulated with spin-canting features by perpendicular fields with respect to the easy axis.
Moreover, the modulation of EL efficiency during these two spin transitions shows the opposite
trend, due to the distinct magneto-resistance responses in these two cases.

In this prototype spin-LED, the air-stable vdW CrSBr is selected as the magnetic medium
with layer-dependent magnetism including ferromagnetic (FM), Ferrimagnetic (FiM) and
antiferromagnetic (AFM) phases28-32. This selection is deliberated based on the unique
exciton/electron-spin interactions in CrSBr as elucidated in recent reports28. Due to the 2D
quantum confinements, strong anisotropy and 2D magnetism, CrSBr exhibits unconventional
light-matter interactions for photoluminescence (PL)33, surface and bulk excitons34,35, exciton
polaritons36-38, exciton-phonon/exciton-magnon coupling39,40 and unique exciton dynamics41.
Moreover, CrSBr also supports distinct spin-charge coupling for spin-dependent charge transfer42
and electrostatic control of spin polarization in heterostructures31. This design is rooted in the
insight that carrier injection can dynamically tune interlayer exchange energy and itinerant
ferromagnetic components in CrSBr, enabling EL to serve as a functional readout of magnetic
phase transitions—filling the gap between magnetic characterization and practical opto-spintronic
devices. It is important to distinguish the operational paradigm of such spin-LEDs from
conventional ones. Typical spin-LEDs encode spin information into the circular polarization of
emitted light43,44. The device we demonstrate encodes the magnetic order state—leveraging spin
transitions—into the emission energy, intensity, and its hysteretic memory, while the output light
remains robustly linearly polarized due to the intrinsic anisotropy of material. This establishes a
distinct mechanism of magnetic-order-modulated EL.

Results
EL characterization in CrSBr

Sample configuration and characterizations. To probe the intrinsic EL properties of CrSBr,
a tunneling LED integrated with a QW structure is designed and fabricated (see Supplementary
Section 1 Fig. S1, S2 for sample preparations). The QW structure consists of a few-layer CrSBr
flake sandwiched between top and bottom graphite (G) electrodes, with upper and lower barrier
layers of hexagonal boron nitride (h-BN) (Fig. 1a). In this device design, electrons and holes are
injected into the CrSBr flake by tunneling through hBN from top and bottom G, respectively (Fig.
1b). This design is crucial as it provides clean interfaces and minimizes defect-induced scattering,
both essential for achieving high-quality optical and electrical performance45-47. As a result, few-
layer CrSBr samples not only show clear PL spectra of bulk (X ) and surface (X ) excitons, but
b s
also more importantly exhibit unambiguous EL spectra as well. Fig. 1c shows the CrSBr thickness-
dependent spectral features of X and X in the device structure, which are consistent with the
b s
previously reported excitonic emissions in CrSBr34. Specifically, the PL features only one peak of
X ~ 1.34 eV (the blue segment) in the bilayer (2L) CrSBr, and starts to embrace another peak of
s
X ~ 1.36 eV (pink segment) in samples with 3-layer (3L) and more layers of CrSBr
b
(Supplementary Section 1 Fig. S3). As the CrSBr thickness increases to 15 layers (15L), the PL
spectrum is dominated by the peak of X . Note here two split peaks of X in the 15L sample may
b s
be due to two X experiencing slightly different dielectric environments34,35. Expectedly, this
s
thickness dependence originates from the layered structure and the AFM orders of CrSBr, making
X
b
highly confined to each individual layer and X
s
extremely sensitive to the thickness and
dielectric environments34.

Observation of EL. With the PL characterizations in these CrSBr LED samples, the EL has
been successfully observed with prominent thickness dependence (Fig. 1d). Apparently, all the EL
spectra are dominated by X , where its peaks are consistent with the PL spectra, but their full-
s
width-at-half-maximum (FWHM) becomes much narrower probably due to the reduced screening
by electric injection and suppressed non-radiative decay channel. As the thickness of CrSBr
increases, the peaks of X also split into two being consistent with the PL. Moreover, statistical
s
analysis of thickness-dependent spectra reveals that the X emission intensity scales linearly with
s
layer number (2–15 layers) in both EL and PL measurements (Supplementary Section 1 Fig. S4)
This linear dependence suggests the excitons at each layer of CrSBr are more likely to recombine
independently with quantum confinements induced by the AFM mediated interlayer interactions34.
More importantly, the consistency of EL infers that LED device structure does not compromise
the AFM mediated interlayer interactions. And the h-BN layers serve as uniform tunnel barriers
that effectively decouple the metal electrodes from the CrSBr flake. However, the EL peak of X
b
is much weaker than the PL at thicker samples even though the peak positions of X are consistent
b
(Fig. 1d insets). This is most likely due to efficient recombination of the injected carriers at the
surface, but reduced recombination of much less injected carriers in the bulk region.

To further probe the EL characteristics, voltage dependence and polarization dependence are
both investigated. The voltage dependence unambiguously demonstrates the tunneling features of
EL, verifying the high quality of the devices and its critical role in the realization of EL. Fig. 1e
demonstrates a sharp increase in EL intensity of 15-layer CrSBr as the applied bias rises from 2 V
to 4.5 V at 2 K, indicating clear tunneling behavior. Fitting analysis of this voltage-dependent EL
reveals the specific trend of nonlinear intensity enhancement (Supplementary Section 2, Fig. S6).
Temperature-dependent EL measurements further highlight the excellent contact of the QW device,
which exhibits near-ohmic behavior at 2 K, with the EL intensity increasing linearly as the
temperature decreases from 130 K to 2 K (see Supplementary Section 2, Fig. S7a). The near
quenching of EL in the 15-layer CrSBr device at approximately 130 K occurs below the Néel
temperature (T ≈ 132 K) because EL intensity depends on magnetic order, carrier injection
N
efficiency, and exciton dynamics rather than T alone. Two key mechanisms drive this quenching:
rising temperature within the antiferromagnetic phase increases the population of incoherent
magnons to strengthen exciton-magnon scattering37,48 and intensifies lattice vibrations to enhance
exciton-phonon coupling49, with the Br-related interlayer phonon mode in multilayer CrSBr—
known for high temperature sensitivity50—further promoting non-radiative exciton relaxation;
meanwhile, the resistance of the h-BN tunnel barrier increases with temperature (see
Supplementary Section 2, Fig. S7b), impeding carrier tunneling into CrSBr and reducing injection
efficiency. To quantify this behavior, we define T as the temperature where EL intensity reaches
EL
5% of its 2 K value, and for the 15-layer device, T is approximately 113 K—lower than T due
EL N
to non-radiative losses and barrier effects. T also varies with layer thickness, which decreases to
EL
around 58 K for 3-layer CrSBr (weaker carrier confinement exacerbates decay) and increases to
approximately 83 K for 9L CrSBr (improved thermal stability of interlayer coupling mitigates
performance loss).

The polarization dependence of EL indicate robust anisotropy, which is resilient to external
magnetic field (B) and has little dependence on CrSBr thicknesses. As shown in Fig. 1f, the EL of
the 15-layer CrSBr device maintains a strong linear polarization that remains invariant under both
in-plane magnetic field B of 0.5 T along the easy axis of b and out-of-plane field B (3 T) along
in out
the hard axis of c. This is consistent with the near-unity linear polarization of PL. Further
calculations of the EL linear polarization ratio ρ= (I0-I90)/(I0+I90) reveal that ρ approaches 100% under 0 T,
B (0.5 T), and B (3 T) (Supplementary Section 2, Fig. S8). Though the EL linear polarization
in out
might be correlated with the in-plane spin orders26, the in-plane anisotropy is not broken down by
the applied magnetic fields. The robust linear polarization of EL in CrSBr devices—resilient to
both in-plane and out-of-plane magnetic fields—exhibits distinct advantages over prior work on
anisotropic 2D optoelectronic materials. For example, transition metal dichalcogenides (TMDs)
often require integration with metal gratings to achieve linearly polarized EL51,52, black
phosphorus shows poor air stability that degrades its anisotropic emission53, and ReSe features
2
relatively weak optical anisotropy54; moreover, the polarization states of these materials are
typically sensitive to external fields, leading to unstable performance. In our CrSBr devices, the
high and field-insensitive linear polarization originates from the material’s intrinsic strong
crystalline anisotropy, which dominates the EL polarization behavior and shields it from external
magnetic field perturbations. This stable anisotropic emission, coupled with the spin-modulated
functionality of the spin-LED, further complements the core advantages of our device architecture.
Moreover, similar EL linear polarization is also observed in 9-layer CrSBr device (see
Supplementary Section 2, Fig. S9), and thus the anisotropy is intrinsic and has little dependence
on CrSBr thicknesses.

EL manipulation by spin-flip transitions

EL hysteresis of peak energies. To monitor the EL by spin-flip transitions, the EL
dependence on the B along the magnetic easy axis of CrSBr (B ∥ b) is firstly investigated in an
in
LED device of 15L CrSBr at 2 K. The evolution of EL spectra is summarized as the field B ∥ b
in
is swept backward from 0.6 T to -0.6 T (Fig. 2a) and forward from -0.6 T to 0.6 T (Fig. 2b). When
B ∥ b is swept to stronger fields around -0.3T and 0.3T, the EL peaks of both X and X undergo
in s b
abrupt redshifts by ~ 20 meV. The redshifts of CrSBr exciton energies are recognized as an
effective indicator for the spin transitions from AFM to FM, where the excitons of FM phase are
smaller than those of AFM phase by ~ 20 meV28,34. Therefore, the abrupt redshifts of ~ 20 meV
are most likely to represent the spin-flip transitions between AFM and FM phases along the easy
b axis. Notably, the magnetic‑field modulation of EL remains observable up to 130 K
(Supplementary Section 2 Fig. S7a), demonstrating the thermal stability of the EL device. The
eventual disappearance of detectable EL modulation at higher temperatures is attributed to the
rapid thermal quenching of the EL intensity due to enhanced non‑radiative recombination, which
masks the magnetic‑order effects before the magnetic transition temperature is reached. Future
improvements in device design—such as interface defect engineering, atomic‑layer‑deposited
passivation layers, or optimized heterostructure configurations—are expected to suppress
non‑radiative channels and thereby extend the operating temperature range toward room
temperature. More strikingly, by extracting the B-dependent peak energies of X for the sweeping
s
loop, the EL peaks demonstrate a pronounced hysteresis of the abrupt redshifts (Fig. 2c, see a
similar hysteresis for the EL peak of X in Supplementary Section 3 Fig. S10). The EL hysteresis
b
of abrupt redshifts is thus smoking-gun evidence to indicate the underlying spin-flip transitions in
the operating LED devices.

To further confirm the spin-flip transitions, the PL spectra of the same device were also
measured under sweeping B ∥ b. The PL spectra show consistent abrupt excitonic redshifts around
in
-0.3 T and 0.3 T (Figs. 2d and 2e), and the B-dependent PL peaks also demonstrate a similar
hysteresis (Fig. 2f). Furthermore, both the EL and PL spectral changes via spin-flip transitions
persist throughout various CrSBr thicknesses, though the magnitude of the abrupt redshifts
diminish progressively with decreasing layers (see Supplementary Section 3, Fig. S11-S15 for 9
L, 6 L, 3 L and 2 L CrSBr devices). The PL hysteresis thus corroborates the spin-transition
mediated exciton energies. It is also noted that the EL hysteresis is more prominent than that of
PL. This might be due to carrier injection-induced modulation of interlayer exchange energy55-57
and the enhancement of the itinerant ferromagnetic component from the carrier injection58,59. For
more details, see Figures S16 and S17 and the related discussion in the Supplementary Information.

EL hysteresis of intensities. Other than the EL peak energies, the EL intensities also show
intriguing hysteresis under sweeping B ∥ b, which is most probably due to the hysteresis
in
magnetoresistance (MR) in the devices. Fig. 2g summarizes the MR measurements of few-layer
CrSBr under sweeping B ∥ b, where the MR decreases with increasing B magnitude and reaches
in
the minimum around -0.3 T and 0.3 T without further changes. By tracking the full sweeping loop
of B
in
∥ b, the MR shows a hysteresis feature which is inherited from the hysteresis of the magnetic
phases. In the magnetic hysteresis, MLR is lower in parallel alignment of magnetic moments in the
FM phase, but becomes larger in antiparallel alignment in the AFM phase60,61. Therefore, this MR
hysteresis could directly manipulate the EL intensities in the studied LED devices.

More surprisingly, the EL intensities demonstrate a similar hysteresis of the X
s
intensities
with the sweeping loop of B ∥ b in the 15 L device, where the intensities are inverse proportional
in
to the MR (Fig. 2h). The AFM phase, which corresponds to higher MR, results in weak EL intensity.
After the spin-flip transition to the FM phase, the lower MR facilitates more efficient carrier
injection, yielding stronger EL intensity. Further analysis shows that the modulation efficiency of
EL by B reaches 48.9%, as discussed in detail in Supplementary Section 3. To illustrate the
in
underlying mechanism of the EL hysteresis, the mechanism schematics is also presented in Fig. 2i
to provide a physical intuition of the spin-order correlated EL intensities.

EL manipulation by spin-canting transitions

Continuous modulation of EL peak energies. To monitor the EL by spin-canting transitions,
the EL dependence on the out-of-plane B along the magnetic hard axis of CrSBr (B ∥ c) is
out
investigated in the device of 15L CrSBr at 2 K. The evolution of EL spectra is summarized as the
field B ∥ c is swept backward from 3.0 T to -3.0 T (Fig. 3a) and forward from -3.0 T to 3.0 T
out
(Fig. 3b). When B ∥ c is swept to stronger fields around -2.0 T and 2.0 T, the EL peaks of X and
out s
X undergo continuous redshifts, which are saturated beyond higher magnetic fields of ~2.0 T or
b
~ -2.0 T. By extracting the B-dependent peak energies of X and X for the sweeping loop, the
s b
redshifts show a general spin-canting feature following (∆𝐸 ∝ 𝐵2 ) (Fig. 3c). For comparisons,
𝑜𝑢𝑡
the PL spectra under the sweep loop of B ∥ c were also measured, showing consistent continuous
out
redshifts between -2.0 T and 2.0 T (Figs. 3d and 3e). The B -dependent PL peaks also
Sout
demonstrate a similar spin-canting feature (Fig. 3f), which is consistent with previous spin-canting
observation28 and corroborates the general feature of spin-canting modulation for both X and X .
s b
Moreover, this spin-canting response of EL is consistently observed across 9-layer, 6-layer and 3-
layer CrSBr (Supplementary Section 4, Fig. S18, S19 and S21), confirming it as an intrinsic
characteristic of the EL manipulation. It is noted that there is a small plateau of the 𝐵 -dependent
𝑜𝑢𝑡
EL peak (X
s
) energies at small magnetic fields (Fig. 3c bottom), which may be due to spin canting
barriers at the interface during the electrical injection. More specifically, in the multi-interface QW
structure employed here, carrier injection occurs across several heterointerfaces. Effects such as
interface contamination or defects, as well as spin-canting scattering and interface resistance, are
inevitably present and collectively increase the energy barrier for magnetic-field-controlled spin
canting, thereby giving rise to the observed plateau in the EL peak shift62,63. Furthermore, the h-
BN encapsulation enhances external screening, which strengthens the magnetocrystalline
anisotropy and stabilizes the magnetic ordering—an effect consistent with prior reports in similar
encapsulated systems64. To validate the interface-dominated origin of this plateau, we performed
thickness-dependent measurements of the EL peak shift under B//c (Supplementary Section 4 Fig.
S20). The plateau width (~0.5 T) remains identical across 3L, 9L, and 15L CrSBr devices,
confirming that this feature is interface-related rather than bulk-thickness-dependent, and
effectively ruling out bulk spin disorder as its cause. This plateau is absent in PL because PL relies
on direct optical excitation of excitons in CrSBr, bypassing interfacial carrier transport and thus
avoiding the spin-canting barrier.

Unexpectedly, the EL efficiency during the spin-canting process exhibits an opposite trend
with respect to spin-flip transition under the sweeping B . Before the saturation field of ∼2.0 T,
out
the MR increases during the spin-canting process with increasing magnetic fields (Fig. 3g), while
the EL intensities decreases with decreasing MR. This indicates that lower carrier injection
efficiency for larger MR, as shown in Fig. 3h. The positive MR under out-of-plane B is an intrinsic
low-temperature property of CrSBr. Below ~30 K, secondary magnetic ordering (or in-plane
domain rotation) induced by hard-axis fields disrupts uniform spin alignment, enhancing carrier-
spin scattering29. Additionally, charge carriers strongly couple to intrinsic magnetic defects
(magnetic polarons); out-of-plane B tilts the spins of these defects toward the field direction,
strengthening exchange interactions and thus enhancing charge carrier scattering65. This behavior
is not contradictory to the negative MR reported in CrSBr-based magnetic tunnel junctions66,67,
where fields applied along the easy axis or strain-induced ferromagnetic coupling dominate
transport via spin-flip transitions or spin-filter effects, respectively. Fig. 3i demonstrates that when
B switches CrSBr from AFM to FM through spin-canting transition, reduced carrier injection
out
efficiency results in weaker EL intensity. Through showing the opposite efficiency trend of EL
efficiency in the spin-flip transition, we take similar modulation analysis and quantify the
manipulation efficiency of EL by B , which reaches 73.8%, as discussed in detail in
out
Supplementary Section 4. Consequently, this device not only provides a novel prototype for
electrically driven light emitters in opto-spintronic devices but also represents a significant step
towards practical application with the large modulation efficiency.

During the preparation of this manuscript, we became aware of two related studies reporting
polarized or polaritonic EL in CrSBr via tunneling-based structures68,69. While these works
demonstrate the feasibility of CrSBr-based light emission, our study achieves a spin-LED in which
the EL itself exhibits pronounced magnetic hysteresis linked to spin-flip transitions and can be
continuously tuned via spin canting. Furthermore, we establish efficient operation down to the
bilayer limit and demonstrate dual-mode magnetic control of both spectral and intensity response
within a designed QW architecture. We demonstrate that electrical injection does not merely
replicate PL behavior but unlocks new functionalities—magnetic memory readout, layer-resolved
control, and spintronic-photonic coupling—thereby providing the essential device concept and
operational principles for future integrated opto-spintronics. These features transform the device
into a functional, non-volatile spin-optoelectronic component, representing a critical step toward
integrated magneto-photonic systems.

In addition, recent reports have demonstrated spin-polarized EL in CrI /TMD heterostructures,
3
where TMDs serve as the light-emitting layer and CrI provides spin polarization. Our work differs
3
fundamentally by using CrSBr as both the magnetic medium and light-emitting layer—eliminating
interface spin scattering and simplifying architecture. Unlike CrI , which only supports out-of-
3
plane spin-flip transitions, CrSBr enables dual spin-transition control (in-plane spin-flip and out-
of-plane spin-canting) for EL modulation with hysteretic/continuous behaviors and a higher
efficiency. CrSBr also exhibits superior air stability compared to air-sensitive CrI
3
. Beyond 2D
systems, our device addresses limitations of traditional magnetic LEDs—low efficiency (<30%),
interface disorder, unstable polarization—by leveraging the intrinsic magnetism of CrSBr to
achieve 73.8% modulation efficiency and near-100% stable linear EL polarization. Prior 2D
magnet-based opto-spintronic devices lacked spin-modulated LEDs, and our work fills this gap by
demonstrating the first prototype with a single 2D magnetic semiconductor down to the bilayer
limit, enabled by strong intrinsic magneto-excitonic interactions.

In summary, the prototype spin-LED, as a core scheme of opto-spintronic devices, has been
realized and manifests spin-transitions modulated EL down to bilayers of vdW CrSBr. Unlike
conventional spin-LEDs that output spin information as circular polarization, our device
transduces magnetic order into tunable emission wavelength and intensity with inherent memory,
representing a magnetic-order-modulated LED paradigm. Particularly, the EL hysteresis
demonstrates that carrier injection can actively engineer interlayer exchange energy in 2D CrSBr.
Besides the spin-order dressed excitonic transitions for the EL spectral resonances, the EL
efficiency is directly determined by the spintronic transport, which shows opposite magnetic-
modulated trends for spin-flip and spin-canting transitions. This study establishes the prototype
device architecture for spin-LED, which essentially merges photonic, electronic, and magnetic
functionalities. Moreover, it also promises many opportunities to develop magnetic sensors,
magnetic tunneling junctions, integrated 2D opto-spintronic chip for neuromorphic computing.

Methods
Synthesis of CrSBr.
CrSBr single crystals were synthesized via chemical vapor transport (CVT, Wuhan Shiwei
Optoelectronic Technology Co., Ltd.). Chromium (III) bromide (CrBr , 99.00% purity, Macklin),
3
sulfur powder (S, 99.95% purity, Aladdin), and Chromium powder (Cr, 99.00% purity, thermo
scientific) were used as precursors. A stoichiometric mixture of CrBr (720 g), S (196 g), and Cr
3
(189 g) was sealed within an evacuated quartz ampoule using an oil-free molecular pump under a
high vacuum. The ampoule was subjected to a controlled thermal gradient. The source zone
temperature was programmed as follows: ramped to 500 °C over 6 h, then to 550 °C over 12 h,
subsequently to 930 °C over 12 h, and finally held at 930 °C for 84 h before cooling naturally to
room temperature. Concurrently, the growth zone temperature profile was: ramped to 570 °C over
6 h and held for 12 h, then increased to 970 °C over 12 h and maintained for 24 h, followed by
cooling to 850 °C over 12 h and holding for 48 h, before natural cooling to room temperature. The
resulting crystals were recovered and stored within an argon-filled glove box upon opening the
ampoule.

Thin flakes of CrSBr were prepared using the scotch magic tape-based mechanical exfoliation
technique. Prior to exfoliation, SiO /Si substrates were treated with oxygen plasma for 10 min to
2
remove surface adsorbates and enhance adhesion. CrSBr crystals were then mechanically
exfoliated directly onto the treated SiO /Si substrates. All exfoliation procedures were performed
2
under ambient conditions at room temperature.

Sample fabrication
QW devices were fabricated using graphite, hBN, and exfoliated CrSBr flakes. Graphite and
hBN crystals were sourced from HQ Graphene. Flake thickness selection for graphite and hBN
followed the criteria established in our previous work70. Both materials were mechanically
exfoliated onto SiO /Si substrates. Dark-field optical microscopy confirmed the flakes possessed
2
clean surfaces and uniform quality, qualifying them for quantum well assembly. CrSBr flakes of
varying layer numbers were initially identified via optical microscopy contrast and subsequently
had their thickness verified by atomic force microscopy. Device assembly was performed on a
transfer stage. A polydimethylsiloxane (PDMS)/polycarbonate (PC) stamp was used to
sequentially pick up the constituent layers (graphite, hBN, CrSBr, hBN, graphite) at 80 °C. The
assembled stack was then transferred onto pre-patterned electrodes. These electrodes were
fabricated by ultraviolet photolithography followed by thermal evaporation of a 5 nm chromium
adhesion layer and a 50 nm gold layer. During the transfer, the PC film was melted onto the
electrode structure. Finally, the completed device was immersed in chloroform to dissolve residual
PC. This was followed by sequential 5-minute immersions in acetone and isopropanol to ensure
the surface remained clean and free of contaminants.

Experimental setup
The experimental setup for PL, EL, and electrical characterization incorporated a closed-loop
cryofree magneto-optical system (attoLDRY 2100) featuring a 9 T superconducting magnet (out-
of-plane) and an attocube piezo-driven xyz translation stage. Optical spectra (PL and EL) were
collected using a WITec Alpha 300R confocal microscope. PL was excited with a 532 nm laser
focused to a spot size of approximately 1 micrometer. Device voltage control was managed by a
Keysight B1500A parameter analyzer. AFM imaging in contact mode was conducted on a Bruker
DIMENSION ICON instrument employing a DDESP-V2 cantilever (force constant: 80 N/m,
resonance frequency: 450 kHz).

Data availability
The data that support the findings of this study are available in the main text and Supplementary
Information. Additional data may be obtained from the corresponding author upon request.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "The authors have made a clear effort to address my previous comments and have added additional experiments and analyses to strengthen their claims. The revision helps clarify several aspects of the device behavior and supports the central conclusions of the manuscript. Nevertheless, some points related to the physical interpretation—particularly concerning the relationship between hysteresis, energy dissipation, and transport-related metrics—would benefit from further clarification. The corresponding suggestions are listed below. After the authors address these issues through a major revision, I believe the work would be much improved and suitable for publication.\n1. Continuing the previous comment 1. While the authors provide several arguments supporting a predominantly magnetic origin of the EL modulation, the current evidence does not fully exclude thickness-dependent injection effects. In particular, although the h-BN layers are designed to act as uniform tunneling barriers, the effective carrier injection into CrSBr may still depend on the electronic structure of the CrSBr layer itself, which is known to evolve with thickness. To further rule out residual injection-related effects (e.g., thickness-dependent effective barriers), the authors are encouraged to provide voltage-dependent EL intensity measurements for devices with different CrSBr thicknesses. A comparison of the EL turn-on behavior (similar to Fig. 1e and Fig. S6) across different layer numbers would serve as a direct control experiment to demonstrate that carrier injection is largely independent of CrSBr thickness, thereby strengthening the conclusion that the observed EL modulation is purely magnetic in origin.\n2. Continuing the previous comment 4. The hysteresis loop area reflects the energy dissipation associated with changes in spin configuration, including spin-flip transitions. The processes are intrinsic to the magnetic spin ordering of the CrSBr layers. In this context, current density and EQE are not the natural parameters governing spin-configuration-related dissipation. Varying the current density at a fixed thickness primarily probes carrier injection and transport, but does not modify the underlying spin configuration responsible for the hysteresis. Therefore, the observation that the hysteresis loop area remains unchanged with current density while EQE decreases does not directly support the conclusion that hysteresis-related dissipation is decoupled from EL efficiency in general. A discussion focusing on thickness-dependent hysteresis would be more physically relevant than a current-density-dependent analysis, since the spin ordering in CrSBr evolves with layer number.", "reviewer_2": "The authors have satisfactorily addressed all of my concerns in the revision. I therefore recommend publication in Nature Communications.", "reviewer_3": "Overall, I find that my specific technical questions have been addressed satisfactorily, and I appreciate the additional data and clarifications provided in the revised manuscript. That said, I want to emphasize that several points raised by other reviewers appear more central to the paper’s impact.\nOne remaining issue for me concerns the interpretation of the electroluminescence hysteresis. While the authors demonstrate convincingly that EL hysteresis is more pronounced than PL hysteresis, the physical origin and broader significance of this difference remain insufficiently explained. In particular, it is still unclear why EL hysteresis is fundamentally distinct from PL hysteresis, rather than simply a manifestation of transport-modulated intensity, and what new insight this provides into spin–exciton coupling or magnetic phase transitions in CrSBr. I encourage the authors to articulate more clearly what is qualitatively new about EL hysteresis compared to PL, beyond the presence of carrier injection.\nFinally, I note that several parts of the rebuttal, including the response to my Q1 and the responses to Reviewer 4 Q1 and Q2, read as highly templated and generic. This makes it difficult to judge whether the authors have fully engaged with the underlying physical concerns, as opposed to providing broadly applicable rebuttal language. A more mechanism-driven discussion that directly addresses the conceptual implications would substantially strengthen the manuscript.", "reviewer_4": "I have read the comments from the authors. I appreciate the efforts the authors made in addressing both the reviewer's concerns regarding certain aspects of the data and the novelty of the work. In my opinion, the puzzling magnetoresistance behavior raised by all reviewers is still not entirely clarified. However, this point is not really essential to the main claims and findings of the paper which are unambiguous (but also somewhat unsurprising). Therefore, I think the paper can be published in Nature Communications.", "reviewer_5": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Point-to-point response (All revisions to the manuscript are marked in blue)\nNOTE:\nFig. + number to represent the figure in the Manuscript.\nFig. S + number to represent the figure in the Supporting Information.\nFig. R + number to represent the figure in the Response.\nReviewer #1\n(Remarks to the Author)\nThe authors have made a clear effort to address my previous comments and have added\nadditional experiments and analyses to strengthen their claims. The revision helps\nclarify several aspects of the device behavior and supports the central conclusions of\nthe manuscript. Nevertheless, some points related to the physical interpretation—\nparticularly concerning the relationship between hysteresis, energy dissipation, and\ntransport-related metrics—would benefit from further clarification. The corresponding\nsuggestions are listed below. After the authors address these issues through a major\nrevision, I believe the work would be much improved and suitable for publication.\n1. Continuing the previous comment 1. While the authors provide several arguments supporting a predominantly magnetic origin of the EL modulation, the current evidence does not fully exclude thickness-dependent injection effects. In particular, although the h-BN layers are designed to act as uniform tunneling barriers, the effective carrier injection into CrSBr may still depend on the electronic structure of the CrSBr layer itself, which is known to evolve with thickness. To further rule out residual injection-related effects (e.g., thickness-dependent effective barriers), the authors are encouraged to provide voltage-dependent EL intensity measurements for devices with different CrSBr thicknesses. A comparison of the EL turn-on behavior (similar to Fig. 1e and Fig. S6) across different layer numbers would serve as a direct control experiment to demonstrate that carrier injection is largely independent of CrSBr thickness, thereby strengthening the conclusion that the observed EL modulation is purely magnetic in origin.\nResponse:\nThank you for your detailed and insightful suggestion. Following your\nrecommendation, we have supplemented more precise voltage-dependent EL\nintensity measurements for devices with different CrSBr thicknesses, as presented\nin new Supplementary Figure S6. It can be clearly observed that the turn-on\nvoltages are all ~2.5 V across devices with 3-layer (2.5 V) to 15-layer (2 V) CrSBr—exhibiting\nnegligible variation. This directly demonstrates that carrier injection is largely\nindependent of CrSBr thickness.\nFigure S6. Voltage-dependent EL intensity of 3-layer (red), 9-layer (yellow) and 15-\nlayer (light blue) CrSBr QW device at 2 K.\nAdditionally, we performed control experiments on a 9-layer CrSBr device\nintegrated with thicker h-BN barriers (Figure R1), and found that the EL turn-on\nvoltage increased significantly to 8 V. This result further confirms that carrier injection\nefficiency is primarily governed by the thickness of the h-BN tunnel barriers rather than\nthe CrSBr layer itself. Collectively, these supplementary experiments effectively rule\nout residual injection-related effects (e.g., thickness-dependent effective barriers) and\nstrongly reinforce our conclusion that the observed EL modulation originates from\nmagnetic effects.\nFigure R1. Voltage-dependent EL intensity of 9-layer CrSBr QW device with thick\nhBN (3.5nm) at 2 K.\n2. Continuing the previous comment 4. The hysteresis loop area reflects the energy dissipation associated with changes in spin configuration, including spin-flip transitions. The processes are intrinsic to the magnetic spin ordering of the CrSBr layers. In this context, current density and EQE are not the natural parameters governing spin-configuration-related dissipation. Varying the current density at a fixed thickness primarily probes carrier injection and transport, but does not modify the underlying spin configuration responsible for the hysteresis. Therefore, the observation that the hysteresis loop area remains unchanged with current density while EQE decreases does not directly support the conclusion that hysteresis-related dissipation is decoupled from EL efficiency in general. A discussion focusing on thickness-dependent hysteresis would be more physically relevant than a current-density-dependent analysis, since the spin ordering in CrSBr evolves with layer number.\nResponse：\nThank you for your constructive and insightful comment. Following your valuable\nsuggestion, we have performed a systematic comparative analysis of the hysteresis\nloop area as a function of CrSBr layer thickness, with the results presented in\nSupplementary Figure R2. Notably, the hysteresis loop area gradually decreases as the\nlayer number reduces from 15-layer, 11-layer to 9-layer CrSBr. This observation\ndirectly confirms that the magnitude of hysteresis is intrinsically correlated with the\nlayer thickness of CrSBr—consistent with the physical picture that spin ordering in\nCrSBr evolves with layer number (e.g., weakened interlayer coupling in thinner layers).\nIn contrast, our previous supplementary experiments under varying current densities\n(0.21–0.69 μA/μm²) did not reveal any noticeable change in the hysteresis loop area,\nfurther validating that carrier injection density does not modulate the underlying spin\nconfiguration responsible for hysteresis.\nFigure R2. Difference in EL energy shift of X during a back-and-forth sweep of\ns\nmagnetic field for (a) 15-layer, (b) 11-layer, (c) 9-layer CrSBr, where 0 T is referenced\nto 0 eV.\nIn the revised Supplementary Information, we have incorporated the thickness-\ndependent hysteresis comparative analysis in Figure S12, (page 12, line 15)：\nSystematic comparison of the EL hysteresis loops for 15-layer (Fig. 2c), 11-layer (Fig.\nS16c) and 9-layer (Fig. S16c) CrSBr reveals that the hysteresis magnitude decreases\nwith decreasing layer thickness of CrSBr — a trend consistent with the physical picture\nthat spin ordering in CrSBr is layer-number dependent, which manifests as the\nweakening of interlayer magnetic coupling in thinner CrSBr flakes.\nReviewer #2\n(Remarks to the Author)\nThe authors have satisfactorily addressed all of my concerns in the revision. I therefore\nrecommend publication in Nature Communications.\nResponse：\nWe sincerely thank the reviewer for the constructive guidance and for recommending\nour work for publication.\nReviewer #3\n(Remarks to the Author)\nOverall, I find that my specific technical questions have been addressed satisfactorily,\nand I appreciate the additional data and clarifications provided in the revised manuscript.\nThat said, I want to emphasize that several points raised by other reviewers appear more\ncentral to the paper’s impact.\nOne remaining issue for me concerns the interpretation of the electroluminescence\nhysteresis. While the authors demonstrate convincingly that EL hysteresis is more\npronounced than PL hysteresis, the physical origin and broader significance of this\ndifference remain insufficiently explained. In particular, it is still unclear why EL\nhysteresis is fundamentally distinct from PL hysteresis, rather than simply a\nmanifestation of transport-modulated intensity, and what new insight this provides into\nspin–exciton coupling or magnetic phase transitions in CrSBr. I encourage the authors\nto articulate more clearly what is qualitatively new about EL hysteresis compared to\nPL, beyond the presence of carrier injection.\nResponse：\nThank the reviewer for the insightful comment regarding the physical origin of the\nenhanced EL hysteresis. We clarify that the fundamental distinction lies in the active\nrole of injected carriers. For PL, the optical excitation generates excitons that act\nprimarily as passive probes of the existing magnetic order. In contrast, EL involves the\ncontinuous injection of spin-polarized electrons and holes through the CrSBr layers.\nThese injected carriers do not merely \"light up\" the material; they actively modulate\ninterlayer exchange interaction⁠1,2⁠.\nThe carrier-mediated modulation of magnetic interactions has been well-\nestablished in 2D vdW magnets: CrI exhibits electric field-tuned FM-AFM balance\n3\nand gate-induced magnetic phase transitions1,3; Cr Ge Te shows gating-modulated\n2 2 6\nmagnetization loops via Fermi level shifts⁠4; CrSBr itself has electrostatic doping-tuned\ninterlayer exchange energy and enhanced hysteresis5. These precedents confirm that\ncarrier doping/injection is a generic pathway to actively manipulate magnetic\ninteractions in vdW magnets.\nThis active modulation of interlayer coupling by carrier injection represents a\nqualitatively new insight into the magnetic phase transitions of CrSBr. Consistent with\nour thickness-dependent observations (Figure S10)—where stronger intrinsic interlayer\ncoupling correlated with larger EL hysteresis—we attribute the enhanced hysteresis to\ncarrier-mediated stabilization of the magnetic order.⁠ While the precise microscopic\ndynamics of these spin-carrier interactions remain a rich area for future inquiry, the\ncurrent data explicitly distinguishes the active nature of EL from the passive readout of\nPL.\nTo ensure these fundamental distinction and qualitatively new insight are clearly\narticulated throughout the revised manuscript, we added targeted statements as shown\nin our response to Comment-2\nFinally, I note that several parts of the rebuttal, including the response to my Q1 and\nthe responses to Reviewer 4 Q1 and Q2, read as highly templated and generic. This\nmakes it difficult to judge whether the authors have fully engaged with the underlying\nphysical concerns, as opposed to providing broadly applicable rebuttal language. A\nmore mechanism-driven discussion that directly addresses the conceptual\nimplications would substantially strengthen the manuscript.\nResponse：\nWe take this critique very seriously. We apologize if our previous responses\nappeared generic; our intent was to provide a concise overview, but we recognize this\nmay have obscured the specific physical insights driving our work. In this revision, we\nhave moved beyond broad descriptions to provide a strictly mechanism-driven\ndiscussion, particularly linking the device performance to the microscopic spin-charge\ninteractions in CrSBr.\nOur selection of CrSBr as the core system is rooted in its unique intrinsic\nproperties that enable CrSBr to serve as both a magnetic medium and a light-\nemitting layer, eliminating the need for additional functional layers. This\nmechanism-driven design is what fundamentally distinguishes our work from prior\nstudies6-10. Our QW structure enables active carrier-mediated modulation of\ninterlayer AFM coupling—amplifying the energy barrier for AFM-FM transitions and\nleading to more prominent EL hysteresis than PL. Its orthorhombic crystal symmetry\nfurther endows biaxial magnetic anisotropy, supporting dual spin-transition pathways:\nin-plane spin-flip (B//b) triggers an AFM-to-FM phase transition with non-volatile\nEL hysteresis, while out-of-plane spin-canting (B//c) enables continuous EL\ntuning—functionalities unattainable in CrI or conventional systems11-13. This\n3\nintegration eliminates interface losses and defect-induced non-radiative recombination,\nachieving a record-high modulation efficiency of 73.8%, near-unity field-insensitive\nlinear polarization, and air stability, thus addressing the long-standing limitations of\nlow efficiency, poor stability, and single-mode control in prior magnetic LEDs12,14,15.\nTo ensure these mechanism-driven innovations are clearly articulated throughout\nthe revised manuscript, we added targeted statements in key sections:\nAbstract (page 2, line 10):\nNotably, the intrinsic carrier-tunable interlayer magnetic coupling in CrSBr enables\nEL to actively amplify magnetic hysteresis (via spin-flip) and continuously tune\nmagnetic order (via spin-canting) with robust anisotropy, establishing a connection\nbetween carrier injection, magnetic phase transitions, and optical emission.\nIntroduction (page 4, line 19):\nThis design is rooted in the insight that carrier injection can dynamically tune\ninterlayer exchange energy and itinerant ferromagnetic components in CrSBr, enabling\nEL to serve as a functional readout of magnetic phase transitions—filling the gap\nbetween magnetic characterization and practical opto-spintronic devices.\nResults (page 10, line 1):\nIt is also noted that the EL hysteresis is more prominent than that of PL. This might be\ndue to carrier injection-induced modulation of interlayer exchange energy3-5 and the\nenhancement of the itinerant ferromagnetic component from the carrier injection16,17.\nConclusion (page 15, line 27):\nUnlike conventional spin-LEDs that output spin information as circular polarization,\nour device transduces magnetic order into tunable emission wavelength and intensity\nwith inherent memory, representing a magnetic-order-modulated LED paradigm.\nParticularly, the EL hysteresis demonstrates that carrier injection can actively engineer\ninterlayer exchange energy in 2D CrSBr.\nThese additions, combined with our focus on mechanism-driven design emphasize\nthat our innovation stems from intrinsic physical interactions rather than external\nmodifications. By intentionally designing a structure to leverage carrier-tunable\nmagnetic propertiesn in CrSBr, we realized a spin-LED with non-volatile hysteretic\ncontrol, continuous analog modulation, and spintronic-photonic integration—\naddressing the long-standing gap between magnetic characterization and functional\nopto-spintronic devices.\nReviewer #4\n(Remarks to the Author)\nI have read the comments from the authors. I appreciate the efforts the authors made in\naddressing both the reviewer's concerns regarding certain aspects of the data and the\nnovelty of the work. In my opinion, the puzzling magnetoresistance behavior raised by\nall reviewers is still not entirely clarified. However, this point is not really essential to the\nmain claims and findings of the paper which are unambiguous (but also somewhat\nunsurprising). Therefore, I think the paper can be published in Nature Communications.\nResponse:\nWe sincerely thank the reviewer for their positive evaluation and recommendation\nfor the publication of our manuscript in Nature Communications. We acknowledge the\nreviewer’s comment on the inherent complexity of the magnetoresistance behavior in\nthis van der Waals magnetic device system, and we intend to further investigate this\nintriguing physical phenomenon in our subsequent work by fabricating more tailored\ndevices and conducting systematic, in-depth characterizations to achieve a\ncomprehensive understanding. We greatly appreciate the reviewer’s judgment that,\ndespite these intricate details of magnetoresistance, the core claims and key findings of\nour work regarding the electroluminescence properties of CrSBr-based spin-LEDs\nremain unambiguous and robust. We are truly grateful for all the constructive feedback\nprovided throughout the review process, which has substantially helped us refine and\nimprove the quality of our manuscript.\nReviewer #5\n(Remarks to the Author)\nI co-reviewed this manuscript with one of the reviewers who provided the listed reports.\nThis is part of the Nature Communications initiative to facilitate training in peer review\nand to provide appropriate recognition for Early Career Researchers who co-review\nmanuscripts.\nResponse：\nWe sincerely thank the reviewer for their dedicated efforts and insightful comments\nthroughout the peer review process. Your valuable input has not only helped us refine\nthe manuscript but also deepened our understanding of the underlying physical\nmechanisms, and we will incorporate these insights into our follow-up research to\nfurther explore the opto-spintronic properties of 2D magnetic semiconductors."}, {"round": 2, "reviewer_comments": {"reviewer_3": "The authors have addressed my previous comments and improved the manuscript through additional discussion and clarification. In particular, the revised text now more clearly distinguishes the roles of EL and PL in probing magnetic phase transitions in CrSBr, emphasizing the potential role of carrier injection in modulating interlayer magnetic coupling. While the microscopic mechanism behind the enhanced EL hysteresis compared to PL remains somewhat speculative, the authors now frame this interpretation more cautiously and provide relevant literature context.\nThe manuscript presents a solid experimental study demonstrating electroluminescence in CrSBr-based vdW heterostructures and its modulation by spin-flip and spin-flop transitions. This represents an interesting and timely advance in the exploration of spin-dependent optoelectronic phenomena in 2D magnetic materials.\nSome aspects of the transport interpretation and the precise microscopic origin of certain effects, such as the enhanced EL hysteresis and the positive magnetoresistance under out-of-plane fields, remain open questions. However, these issues do not undermine the main experimental observations or the central claims of the work.\nOverall, I find that the authors have adequately addressed my concerns, and I believe the manuscript is suitable for publication in Nature Communications.", "reviewer_5": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": ""}]

Decision letter