Probing the Spin Dimensionality in Single‐Layer CrSBr Van Der Waals Heterostructures by Magneto‐Transport Measurements

Abstract

2D magnetic materials offer unprecedented opportunities for fundamental and applied research in spintronics and magnonics. Beyond the pioneering studies on 2D CrI 3 and Cr 2 Ge 2 Te 6 , the field has expanded to 2D antiferromagnets exhibiting different spin anisotropies and textures. Of particular interest is the layered metamagnet CrSBr, a relatively air-stable semiconductor formed by antiferromagnetically-coupled ferromagnetic layers (T c ∼150 K) that can be exfoliated down to the single-layer. It presents a complex magnetic behavior with a dynamic magnetic crossover, exhibiting a low-temperature hiddenorder below T*∼40 K. Here, the magneto-transport properties of CrSBr vertical heterostructures in the 2D limit are inspected. The results demonstrate the marked low-dimensional character of the ferromagnetic monolayer, with short-range correlations above T c and an Ising-type in-plane anisotropy, being the spins spontaneously aligned along the easy axis b below T c . By applying moderate magnetic fields along a and c axes, a spin-reorientation occurs, leading to a magnetoresistance enhancement below T*. In multilayers, a spin-valve behavior is observed, with negative magnetoresistance strongly enhanced along the three directions below T*. These results show that CrSBr monolayer/bilayer provides an ideal platform for studying and controlling field-induced phenomena in two-dimensions, offering new insights regarding 2D magnets and their integration into vertical spintronic devices.

Spin Waves and Magnetic Exchange Hamiltonian in CrSBr

“…Because the CrSBr semiconducting gap is 1.25(7) eV [ 6 ] (14500 K), the effects of thermally populated conduction‐mediated exchange will be very minor between 5 and 300 K. Some exchange constant shifts with lattice expansion is possible, but such effects will also be minor. [ 26 ] Therefore we expect the magnetic exchange constants in Table 1 can be considered approximately correct at all temperatures below 300 K.…”

Sensing the Local Magnetic Environment through Optically Active Defects in a Layered Magnetic Semiconductor

“…35 This has the advantage that optically clean signatures and magnetic orderings that mimic mono-or bilayer CrSBr can be conveniently probed in disorder-free, high-quality multilayer crystals. 35 The magnetic phase diagram of CrSBr is rich and displays a low-temperature magnetic order that emerges at a critical temperature of T D = 30−40 K. 31,33,36,37 This magnetic order has been observed consistently in magnetic susceptibility and magneto-transport measurements throughout all reported crystals. The origin of this magnetic signature is still under debate, but has been speculated to arise from crystal defects.…”

Magnon Straintronics in the 2D van der Waals Ferromagnet CrSBr from First-Principles

“…While a tends to elongate due to an unconventional expansion when the temperature decreases from 260 K to the so-called spin-freezing temperature T * ≈ 40 K, both b and c lattice parameters become shorter. Intriguingly, these trends lead to a progressive enhancement of J 1 , J 2 , and J 3 …”

“…Intriguingly, these trends lead to a progressive enhancement of J 1 , J 2 , and J 3 . 35 In order to understand the electronic and magnetic structure of single-layer CrSBr, we perform first-principles calculations including spin−orbit coupling (SOC) (see the Methods section). The DFT+U electronic band structure and density of states (DOS) are plotted in Figure S1.…”