Air-Stable and Layer-Dependent Ferromagnetism in Atomically Thin van der Waals CrPS₄

Abstract

Ferromagnetism in two-dimensional materials presents a promising platform for the development of ultrathin spintronic devices with advanced functionalities. Recently discovered ferromagnetic van der Waals crystals such as CrI3, readily isolated two-dimensional crystals, are highly tunable through external fields or structural modifications. However, there remains a challenge because of material instability under air exposure. Here, we report the observation of an air-stable and layer-dependent ferromagnetic (FM) van der Waals crystal, CrPS4, using magneto-optic Kerr effect microscopy. In contrast to the antiferromagnetic (AFM) bulk, the FM out-of-plane spin orientation is found in the monolayer crystal. Furthermore, alternating AFM and FM properties observed in even and odd layers suggest robust antiferromagnetic exchange interactions between layers. The observed ferromagnetism in these crystals remains resilient even after the air exposure of about a day, providing possibilities for the practical applications of van der Waals spintronics.

Metal Site Substitution and Role of the Dimer on Symmetry Breaking in FePS3 and CrPS4 under Pressure

“…It is worth mentioning that the choice of r 2 SCAN pushes the position of P c2 closer to the experimentally observed value of 16 GPa. Note that, because our choice of computational unit cells includes only one CrPS 4 layer, our ferromagnetic solution at low-pressure is consistent with a recently reported A-type antiferromagnetic order …”

Limited Ferromagnetic Interactions in Monolayers of MPS3 (M = Mn and Ni)

“…Although for most of the 3d doping, the Mn–Mn and the Ni–Ni magnetic couplings remain AFM, in the case of Cr doping, the AFM exchanges between the magnetic atoms of the host turn into FM ones. 89 Thus, we performed DFT + U calculations for 25% concentration of the magnetic dopants (X = Cr, Mn, and Ni) in the hosts of NiPS 3 and MnPS 3 . We have employed various structural arrangements of the atoms (see Figure 4 ) and collinear spin configurations such as AFM Neel (AFM-N), zigzag (AFM-z), stripy (AFM-s), and FM case.…”

“…In particular, at low doping concentration, the main exchange couplings are the magnetic exchanges between the host magnetic atoms ( J i M for i = 1, 2, 3) and between the host impurity atoms ( J i MX for i = 1, 2, 3). Although for most of the 3d doping, the Mn–Mn and the Ni–Ni magnetic couplings remain AFM, in the case of Cr doping, the AFM exchanges between the magnetic atoms of the host turn into FM ones . Thus, we performed DFT + U calculations for 25% concentration of the magnetic dopants (X = Cr, Mn, and Ni) in the hosts of NiPS 3 and MnPS 3 .…”

Role of External Stimuli in Engineering Magnetic Phases and Real-Time Spin Dynamics of Co/Mn Oxides

“…Also, CrPS 4 was demonstrated to be air stable because of its multibonded complex crystal structure and chemical composition. 30 Exploring 2D metal oxides as 2D magnets allows us to further achieve different magnetic materials with high stability and tunable magnetic moment, as they can be synthesized by both bottom-up and top-down approaches. Successful chemical vapor deposition (CVD) growth of VO 2 monolayer 34 or etching of 2D Fe 2 O 3 35,36 are examples of the robustness of synthesis processes of these systems.…”

“…have been found to be extremely unstable and can degrade rapidly in the presence of air or sunlight . Thus, to prevent the degradation process, often these systems are synthesized and analyzed in a glovebox in an oxygen-free environment or sandwiched between other stable layered materials to gain stability, which in turn limits their use. , Magnetic systems like 1-T phases of transition-metal dichalcogenides (i.e., VS 2 ) remains in a metastable phase, thus they also need a substrate material to stabilize them in their magnetic state, as the stable 2-H phases of these systems are nonmagnetic in nature. Though the tellurides phases of these systems are relatively more air stable (e.g., CrTe 2 ), they still need a substrate material to stabilize them …”