Observation of nonreciprocal magnetophonon effect in nonencapsulated few-layered CrI ₃

Abstract

“Magneto-optical” effect refers to a rotation of polarization plane, which has been widely studied in traditional ferromagnetic metal and insulator films and scarcely in two-dimensional layered materials. Here, we uncover a new nonreciprocal magnetophonon Raman scattering effect in ferromagnetic few-layer CrI3. We observed a rotation of the polarization plane of inelastically scattered light between −20o and +60o that are tunable by an out-of-plane magnetic field from −2.5 to 2.5 T. It is experimentally observed that the degree of polarization can be magnetically manipulated between −20 and 85%. This work raises a new magneto-optical phenomenon and could create opportunities of applying two-dimensional ferromagnetic materials in Raman lasing, topological photonics, and magneto-optical modulator for information transport and storage.

Strong intrinsic room-temperature ferromagnetism in freestanding non-van der Waals ultrathin 2D crystals

“…Intrinsic room-temperature 2D ferromagnetism in ultrathin two-dimensional (2D) crystals is strongly suppressed and rarely observed. Recent efforts to explore the ferromagnetism in ultrathin 2D crystals have revealed intrinsic ferromagnetism in mechanically exfoliated Cr 2 Ge 2 Te 6 , CrI 3 , and Fe 3 GeTe 2 few-layer crystals, but the ferromagnetic ordering only exists significantly far below room temperature [2][3][4][5][6][7][8][9] . Moreover, most intrinsic ultrathin ferromagnetic 2D crystals have a van der Waals structure and are often exfoliated mechanically by tape [10][11][12][13] .…”

Low Energy Electrodynamics of CrI3 Layered Ferromagnet

“…However, the magnitude of the observed optical-gap energy-shift across the ferromagnetic transition cannot be simply related to any magnetic energy scale. These results suggest that the electronic gap hardening should be related to nontrivial electron-magnetic interactions 24,27,29,33 , leading to a complex picture of the CrI 3 material equilibrium response.…”

“…Here, ferromagnetism may sustain novel phases of matter, like the Quantum Hall Effect (QHA) 16,17 or the spin liquid state 18,19 , opening numerous opportunities for magnetooptical applications [20][21][22] . Moreover, bulk layered vdW magnets can be exploited as substrates, interfacial layers and tunnel barriers for engineering magnetic proximity effects and designing novel spintronic applications 23,24 . Chromium trihalide CrI 3 has been shown to be a cleavable magnetic material with a great tunability of its magnetic properties with thickness [25][26][27] .…”

“…Remarkably, few-layer CrI 3 has been proved to host anti-ferromagnetic order between the layers, with a Néel critical temperature of 45 K and a monoclinic stacking 26 . CrI 3 has been theoretically predicted 29,30 to host strong interactions among electronic, phononic and magnetic degrees of freedom, including a strong spin-orbit coupling (SOC) [31][32][33] , with the appearance of exotic responses like nonreciprocal magneto-electric effects 24,34,35 . As a result, CrI 3 is a candidate material to host subtle, low energy, emergent phases of matter 36,37 .…”

Multiwavelength magnetic coding of helical luminescence in ferromagnetic 2D layered CrI3

“…The emergence of long-range ferromagnetic orders in two-dimensional (2D) van der Waals (vdW) ferromagnetic (FM) material has provided a new avenue for creating on-chip lasers, isolators, and modulators for silicon photonics toward information processing and transmission through magneto-exciton coupling ( Deng et al., 2018 ; Gong et al., 2017 ; Huang et al., 2017 ; Liu et al., 2020 , 2021 ; Mak et al., 2019 ; Song et al., 2018 ; Sun et al., 2019 ). The magnetic orders can be switched between FM and atomic force microscope (AFM) states by magnetic field ( Klein et al., 2018 ; Zhong et al., 2017 ), electric gating ( Huang et al., 2018 ; Jiang et al., 2018a , 2018b ; Zhang et al., 2020 ), electrostatic doping ( Jiang et al., 2018a ; Zheng et al., 2020 ), and hydrostatic pressure ( Li et al., 2019 ; Song et al., 2019 ), which empower a pivotal foundation for realizing magnetic and electric control of magneto-optical coupling for information transfer.…”