Colossal Magnetization and Giant Coercivity in Ion-Implanted (Nb and Co) MoS2 Crystals

Realization of High Magnetization in Artificially Designed Ni/NiO Layers through Exchange Coupling

High-magnetization materials play crucial roles in various applications. However, the past few decades have witnessed a stagnation in the discovery of new materials with high magnetization. In this work, Ni/NiO nanocomposites are fabricated by depositing Ni and NiO thin layers alternately, followed by annealing at specific temperatures. Both the as-deposited samples and those annealed at 373 K exhibit low magnetization. However, the samples annealed at 473 K exhibit a significantly enhanced saturation magnetization exceeding 607 emu cm-3 at room temperature, surpassing that of pure Ni (480 emu cm-3 ). Material characterizations indicate that the composite comprises NiO nanoclusters of size 1-2 nm embedded in the Ni matrix. This nanoclustered NiO is primarily responsible for the high magnetization, as confirmed by density functional theory calculations. The calculations also indicate that the NiO clusters are ferromagnetically coupled with Ni, resulting in enhanced magnetization. This work demonstrates a new route toward developing artificial high-magnetization materials using the high magnetic moments of nanoclustered antiferromagnetic materials.

Recent progresses on ion beam irradiation induced structure and performance modulation of two-dimensional materials

Two-dimensional (2D) materials are receiving significant attention for both fundamental research and industrial applications due to their unparalleled properties and wide application potential. In this case, the controllable modulation of their structures and properties is essential for the realization and further expansion of their applications. Accordingly, ion beam irradiation techniques, with large scope to adjust parameters, high manufacturing resolution, and a series of advanced equipment being developed, have been demonstrated to have obvious advantages in manipulating the structure and performance of 2D materials. In recent years, many research efforts have been devoted to uncovering the underlying mechanism and control rules regarding ion irradiation induced phenomena in 2D materials, aiming at fulfilling their application potential as soon as possible. Herein, we review the research progress in the interaction between energetic ions and 2D materials based on the energy transfer model, type of ion source, structural modulation, performance modification of 2D materials, and then their application status, aiming to provide useful information for researchers in this field and stimulating more research advances.

Ferromagnetic single-atom spin catalyst for boosting water splitting

Heterogeneous single-atom spin catalysts combined with magnetic fields provide a powerful means for accelerating chemical reactions with enhanced metal utilization and reaction efficiency. However, designing these catalysts remains challenging due to the need for a high density of atomically dispersed active sites with a short-range quantum spin exchange interaction and long-range ferromagnetic ordering. Here, we devised a scalable hydrothermal approach involving an operando acidic environment for synthesizing various single-atom spin catalysts with widely tunable substitutional magnetic atoms (M₁) in a MoS₂ host. Among all the M₁/MoS₂ species, Ni₁/MoS₂ adopts a distorted tetragonal structure that prompts both ferromagnetic coupling to nearby S atoms as well as adjacent Ni₁ sites, resulting in global room-temperature ferromagnetism. Such coupling benefits spin-selective charge transfer in oxygen evolution reactions to produce triplet O₂. Furthermore, a mild magnetic field of ~0.5 T enhances the oxygen evolution reaction magnetocurrent by ~2,880% over Ni₁/MoS₂, leading to excellent activity and stability in both seawater and pure water splitting cells. As supported by operando characterizations and theoretical calculations, a great magnetic-field-enhanced oxygen evolution reaction performance over Ni₁/MoS₂ is attributed to a field-induced spin alignment and spin density optimization over S active sites arising from field-regulated S(p)-Ni(d) hybridization, which in turn optimizes the adsorption energies for radical intermediates to reduce overall reaction barriers.

The Lattice Distortion-Induced Ferromagnetism in the Chemical-Bonded MoSe2/WSe2 at Room Temperature

Ferromagnetism to non-ferromagnetism transition is detected in a chemically bonded MoSe[Formula: see text]/WSe[Formula: see text] powder with different thermal annealing temperatures. All samples exhibit ferromagnetism and Raman redshift, except for the 1100 °C thermally annealed sample in which the MoSe[Formula: see text] and WSe[Formula: see text] are thermally dissociated and geometrically separated. The element analysis reveals no significant element ratio difference and detectable magnetic elements in all samples. These results support that, in contrast to the widely reported structure defect or transition element dopant, the observed ferromagnetism originates from the structure distortion due to the chemical bonding at the interface between MoSe[Formula: see text] and WSe[Formula: see text].

Tunable and Robust Near-Room-Temperature Intrinsic Ferromagnetism of a van der Waals Layered Cr-Doped 2H-MoTe2 Semiconductor with an Out-of-Plane Anisotropy

The intrinsically nonmagnetic feature of van der Waals (vdW) layered transition-metal dichalcogenide (TMDC) semiconductors limits the spintronic applications of these semiconductors. In this paper, we demonstrate a facile Te flux strategy to induce intrinsic ferromagnetism in the vdW layered 2H-MoTe₂ semiconductor by magnetic chromium (Cr) doping. The Curie temperature (T_c) and saturation magnetization (M_s) can be well tuned by adjusting the Cr doping concentration. A notable T_c up to 275 K can be achieved for the vdW layered Cr-doped 2H-MoTe₂ bulk crystals, which is much higher than that of recently reported van der Waals ferromagnetic semiconductors (T_c is mostly less than 70 K), in contrast to the diamagnetic feature of the pristine MoTe₂. Meanwhile, the highest M_s of the vdW layered Cr-doped 2H-MoTe₂ bulk crystals can reach 4.78 emu g^-1, which is stronger than most values reported for magnetic-element-doped van der Waals materials. In addition, all of the as-grown semiconducting Cr-doped 2H-MoTe₂ (Cr-2H-MoTe₂) single crystals display a large magnetic anisotropy with an out-of-plane easy axis of magnetization. The observed ferromagnetism in the Cr-2H-MoTe₂ has intrinsic characteristics, which can be mainly attributed to the spin polarization caused by Cr doping as confirmed by the density functional theory (DFT) calculations. Our approach offers an avenue to tune the ferromagnetism in the vdW layered semiconductor and explore its diverse spintronic and magnetoelectric applications.