Atomistic spin textures on-demand in the van der Waals layered magnet CrSBr

Abstract

Controlling magnetism in low dimensional materials is essential for designing devices that have feature sizes comparable to several critical length scales that exploit functional spin textures, allowing the realization of low-power spintronic and magneto-electric hardware. [1] Unlike conventional covalently-bonded bulk materials, van der Waals (vdW)-bonded layered magnets [2-4] offer exceptional degrees of freedom for engineering spin textures. [5] However, their structural instability has hindered microscopic studies and manipulations. Here, we demonstrate nanoscale structural control in the layered magnet CrSBr creating novel spin textures down to the atomic scale. We show that it is possible to drive a local structural phase transformation using an electron beam that locally exchanges the bondings in different directions, effectively creating regions that have vertical vdW layers embedded within the horizontally vdW bonded exfoliated flakes. We calculate that the newly formed 2D structure is ferromagnetically ordered in-plane with an energy gap in the visible spectrum, and weak antiferromagnetism between the planes. Our study lays the groundwork for designing and studying novel spin textures and related quantum magnetic phases down to singleatom sensitivity, potentially to create on-demand spin Hamiltonians probing fundamental concepts in physics, [6-10] and for realizing high-performance spintronic, magneto-electric and topological devices with nanometer feature sizes. [11,12]

The bulk van der Waals layered magnet CrSBr is a quasi-1D quantum material

“…1b). [31] The strong electronic anisotropy is directly apparent from our 1L, 2L and bulk density functional theory (DFT-GW ) calculation (see Fig. 1c-e).…”

“…CrSBr combines several particularly interesting properties. [23][24][25][26][27][28][29][30][31][32][33] It is a semiconductor with an energy gap of ∼ 1.5 eV. [25,27] It is also an Atype antiferromagnet (AFM) with the magnetic easyaxis along the b-direction and a high Néel temperature of T N ∼ 132 K. [24,27] A number of recent works have shown structural phase transformations, [31] magnetooptical [29] and magneto-transport [27,32,33] properties and exciton-magnon coupling.…”

“…[23][24][25][26][27][28][29][30][31][32][33] It is a semiconductor with an energy gap of ∼ 1.5 eV. [25,27] It is also an Atype antiferromagnet (AFM) with the magnetic easyaxis along the b-direction and a high Néel temperature of T N ∼ 132 K. [24,27] A number of recent works have shown structural phase transformations, [31] magnetooptical [29] and magneto-transport [27,32,33] properties and exciton-magnon coupling. [34] Understanding the underlying electronic structure, the quasi-particles and their mutual couplings is key to engineering magnetic properties in CrSBr.…”

The first- and second-order magneto-optical effects and intrinsically anomalous transport in 2D van der Waals layered magnets CrXY (X = S, Se, Te; Y = Cl, Br, I)

“…Crystal, magnetic, and electronic structures Figure 2 shows the crystal structure of vdW layered materials CrXY (X = S, Se, Te; Y = Cl, Br, I). One can see that CrXY has a rectangular 2D primitive cell, in which a ML is made of two buckled planes of CrX sandwiched by two Y sheets, and a BL is formed by two MLs with the AA stacking order referring to experimental works [11,19,20,57]. The relaxed lattice constants of ML and BL structures are collected in supplemental Tab.…”

Dynamic Magnetic Crossover at the Origin of the Hidden-Order in van der Waals Antiferromagnet CrSBr

“…Given the in-plane magnetization, this hints towards the presence of uniaxial anisotropy within the layers. The 2D character of the magnetic order in CrSBr in spite of the three-dimensional antiferromagnetic configuration is understood from the weak coupling across the van der Waals gap, as reflected in the low exchange coupling constants obtained by first principle calculations 24,33 . The weak interlayer coupling is also reflected in the occurrence of a low field meta-magnetic transition, first acting through decoupling of the ferromagnetic (FM) layers along the c-axis, as discussed below.…”