Density Functional Theory Study of Controllable Optical Absorptions and Magneto-Optical Properties of Magnetic CrI₃ Nanoribbons: Implications for Compact 2D Magnetic Devices

Abstract

A chromium triiodide (CrI3) monolayer has an interesting ferromagnetic ground state. In this work, we calculate band structures and magnetic moments of tensile-strained and bent zigzag CrI3 nanoribbons with density functional theory. The edge iodine atoms form flat low-lying conduction bands and couple with chromium atoms ferromagnetically, while the non-edge iodine atoms weakly couple antiferromagnetically. Narrow CrI3 nanoribbons have two locally stable magnetic moment orientations, namely, out-of-plane and in-plane (along the nanoribbon periodic direction) configurations. This enables four magnetization states in CrI3 nanoribbons, including two out-of-plane ones (up and down) and two in-plane ones (forward and backward along the nanoribbon periodical direction), increasing the operating controllability. Based on the one-dimensional Ising spin chain model, the spin correlation length of the narrow CrI3 nanoribbon is estimated to be about 10 Å at its estimated Curie temperature of 27 K, which is lower than the measured 45 K of the monolayer CrI3. The optical absorption and magneto-optical properties of CrI3 nanoribbons are investigated with many-body perturbation GW-BSE (Bethe–Salpeter equation), including magnetic dichroism and Faraday and magneto-optical Kerr effects. The low-energy dark excitons are mainly from transitions between electrons and holes with unlike spins and are non-Frenkel-like, while the bright excitons have mixed spin configurations. The intrinsic lifetime of excitons can be over one nanosecond, suitable for quantum information processes. Tensile strains and bending manifestly modulate the absorption spectra and magneto-optical properties of CrI3 nanoribbons within a technologically important photon energy range of ∼1.0–2.0 eV. The CrI3 nanoribbons can be used in 1D or 2D magnetic storage nanodevices, tunable magnetic optoelectronics, and spin-based quantum information controls.

Nickel-Induced Reduced Graphene Oxide Nanoribbon Formation on Highly Ordered Pyrolytic Graphite for Electronic and Magnetic Applications

“…In the medical field, nanoribbons offer potential for controlled drug delivery and improvements in magnetic imaging . In magnetic catalysis, they can act as catalysts, facilitating specific chemical reactions, and display capability in the fabrication of advanced magnetic sensors. , In magnetic information storage, the improved properties of nanoribbons contribute to more efficient systems . In addition, they have significant potential in spin electronics, promoting advances in spintronics devices .…”

Spin-polarization anisotropy controlled by bending in tungsten diselenide nanoribbons and tunable excitonic states

“…Nanoribbons are interesting, reduced forms of 2D layered materials. [18][19][20][21][22][23][24][25][26] Compared with their 2D counterparts, they have more spatial confinement effects and rich edge states, making Department of Physics, Temple University, Philadelphia, PA 19122, USA. E-mail: hongtang@temple.edu † Electronic supplementary information (ESI) available: Technical note 1 for spinpolarization anisotropy analyses for A12WSe 2 and A7WSe 2 nanoribbons, note 2 for the d-orbital decomposition analyses for A13WSe 2 , Table S1 for the five observations to the band structure map of the d-orbital decomposition of the spin-polarization along the x and y axes for the A13WSe 2 nanoribbon under different bending conditions, note 3 for the k-grid convergence test of the optical absorption spectrum, Fig.…”

“…20 The carbon atoms in each edge of graphene zigzag nanoribbons (GZNRs) are ferromagnetically coupled, while the inter-edge coupling changes from antiferromagnetic in narrow semiconductive GZNRs to ferromagnetic in wide metallic GZNRs. 19 Tang et al 21 showed that the direction of magnetization in CrI 3 nanoribbons can be stably aligned both out-of-plane and parallel to the ribbon axis, increasing their operating controllability. Also, the rich exciton states are shown in SiC, 22 MoS 2 , 23 black phosphorene, 24 and CrI 3 nanoribbons, 21 and the exciton states can be tuned by bending or strains in the nanoribbons.…”

“…19 Tang et al 21 showed that the direction of magnetization in CrI 3 nanoribbons can be stably aligned both out-of-plane and parallel to the ribbon axis, increasing their operating controllability. Also, the rich exciton states are shown in SiC, 22 MoS 2 , 23 black phosphorene, 24 and CrI 3 nanoribbons, 21 and the exciton states can be tuned by bending or strains in the nanoribbons.…”

“…Nanoribbons are interesting, reduced forms of 2D layered materials. 18–26 Compared with their 2D counterparts, they have more spatial confinement effects and rich edge states, making them rife of new functionalities and attractive for applications in compact nanoelectronics, magnetic, optoelectronic, and band-topology based electronic and quantum information devices. 18,19 MoS 2 zigzag nanoribbons were calculated as metallic and with ferromagnetic edges.…”