Layered Antiferromagnetism Induces Large Negative Magnetoresistance in the van der Waals Semiconductor CrSBr

Abstract: The recent discovery of magnetism within the family of exfoliatable van der Waals (vdW) compounds has attracted considerable interest in these materials for both fundamental research and technological applications. However current vdW magnets are limited by their extreme sensitivity to air, low ordering temperatures, and poor charge transport properties. Here we report the magnetic and electronic properties of CrSBr, an air-stable vdW antiferromagnetic semiconductor that readily cleaves perpendicular to the stacking axis. Below its N\'{e}el temperature, $T_N = 132 \pm 1$ K, CrSBr adopts an A-type antiferromagnetic structure with each individual layer ferromagnetically ordered internally and the layers coupled antiferromagnetically along the stacking direction. Scanning tunneling spectroscopy and photoluminescence (PL) reveal that the electronic gap is $\Delta_E = 1.5 \pm 0.2$ eV with a corresponding PL peak centered at $1.25 \pm 0.07$ eV. Using magnetotransport measurements, we demonstrate strong coupling between magnetic order and transport properties in CrSBr, leading to a large negative magnetoresistance response that is unique amongst vdW materials. These findings establish CrSBr as a promising material platform for increasing the applicability of vdW magnets to the field of spin-based electronics.

Insights into Layered Antiferromagnetism and Giant Negative Magnetoresistance of CrSBr

This paper presents an examination of the magnetic and electronic properties of Chromium Sulfur Bromide (CrSBr), a van der Waals (vdW) antiferromagnetic semiconductor. The study provides significant insights into how layered antiferromagnetism influences the magnetoresistance properties of CrSBr, demonstrating a robust coupling between its magnetic order and electronic transport characteristics.

CrSBr's structure comprises ferromagnetically aligned layers that couple antiferromagnetically along the stacking axis, inducing a pronounced negative magnetoresistance (nMR) that exceeds 40%. This nMR is unique compared to typical metallic magnetic materials, which typically exhibit <5% magnetoresistance, and dilute magnetic semiconductors, which usually show around ~15%. The high Néel temperature (Tₙ = 132 ± 1 K) further distinguishes CrSBr from many other vdW materials, which tend to have lower magnetic transition temperatures and stability vulnerabilities under ambient conditions.

The experimental approach in the study employs both magnetotransport and scanning SQUID magnetometry to investigate magnetic susceptibility and magneto-electronic behavior. Several crystallographic axes of CrSBr were explored, and measurements reveal anisotropy features consistent with the easy magnetic axis being along the b-axis. Saturation magnetization demonstrates the anticipated first-order AF-FP spin-flip transition along the b-axis, confirming the robust antiferromagnetic nature of CrSBr.

Noteworthy numerical results include the electron band gap of ΔE = 1.5 ± 0.2 eV and photoluminescence peak at 1.25 ± 0.07 eV, highlighting CrSBr as a direct gap semiconductor. These values match scanning tunneling spectroscopy (STS) and photoluminescence observations, further validating CrSBr’s electron-doped characteristics under various experimental conditions.

The implications of these findings are substantial for the advancement of spintronic devices and two-dimensional magnetism. CrSBr’s strong negative magnetoresistance and high magnetic ordering temperature position it as a candidate for spin-based electronics, which benefit from enhanced speed, density, and energy efficiency through spin-polarized transport. Additionally, its air stability and cleavability promise practical device applications, offering an opportunity to overcome the inherent limitations of current vdW materials.

Moving forward, CrSBr opens prospects for theoretical and practical advancements in the synthesis of magnetic semiconductors that manage both charge and spin properties. Its ability to combine high magnetic ordering with semiconducting transport features presents a pivotal step in designing materials that can be adapted for various spintronic and magneto-optical applications. Further research may explore tailoring the semiconductor’s magnetic interactions at atomic-layer levels or integrating multi-functional heterostructures to capitalize on CrSBr's unique features for sophisticated electronic architectures.