Ni-Intercalated NbSe Shows Magnetic Frustration with 23.5 K Ordering and −137 K Curie–Weiss Temperature

The interplay between magnetism and superconductivity in layered materials receives significant attention, and recent work by Ashutosh S. Wadge, Alexander Kazakov, and Xujia Gong, alongside colleagues at the International Research Centre MagTop, Institute of Physics, Polish Academy of Sciences, reveals a dramatic shift in electronic behaviour within nickel-intercalated niobium diselenide. The team demonstrates that introducing nickel fundamentally alters the properties of this material, suppressing both charge density waves and superconductivity, and establishing a magnetically frustrated state. Through a combination of magnetic measurements and angle-resolved photoemission spectroscopy, researchers discovered a reconstructed electronic structure with a new electron pocket, indicating a substantial change to the material’s Fermi surface. This achievement provides crucial insight into how partial intercalation and disorder can drive complex magnetic order and reshape the electronic landscape in low-dimensional materials, positioning nickel niobium diselenide as a compelling example of magnetically frustrated, non-superconducting behaviour.

Ni-Intercalated NbSe2 Exhibits Altermagnetism

This study reveals a novel magnetic state, altermagnetism, in nickel-intercalated niobium diselenide, a two-dimensional material with potential applications in future technologies. Researchers investigated nickel niobium selenide, inserting nickel atoms between the layers of the material and observing a unique combination of magnetic behaviors not seen in conventional magnets. This altermagnetism arises from a delicate balance between electron-driven and atomic-driven magnetic moments, resulting in a non-collinear magnetic order where magnetic moments do not align in a simple pattern. The team employed advanced experimental techniques to characterize the material.

X-ray diffraction confirmed the successful insertion of nickel atoms into the niobium diselenide structure, while atomic force microscopy verified the layered arrangement. Magnetic measurements revealed the complex magnetic behavior indicative of altermagnetism, including a non-zero magnetization even without an external magnetic field. Angle-resolved photoemission spectroscopy probed the electronic structure, revealing how electrons behave within the material and contribute to the observed magnetism. These experimental findings were supported by theoretical calculations providing insights into the electronic structure and magnetic properties.

The results demonstrate that the nickel atoms significantly alter the electronic band structure of niobium diselenide, creating new electronic bands and modifying existing ones. The altered electronic structure exhibits spin polarization, meaning electrons with different spins have different energies, contributing to the magnetic order. The team proposes that the nickel atoms act as magnetic moments interacting with the conduction electrons in niobium diselenide, leading to the observed non-collinear magnetic order. Furthermore, the study suggests the possibility of magnetic polarons forming, quasiparticles that could contribute to the altermagnetic behavior.

This discovery adds to the growing list of materials exhibiting altermagnetism and opens new avenues for exploring spintronic devices, which utilize the spin of electrons for information storage and processing. The research highlights the potential for engineering novel magnetic states in two-dimensional materials by carefully controlling their composition and structure. Future research will focus on detailed studies of the magnetic structure using neutron scattering, investigating the effects of different nickel concentrations, and exploring the possibility of tuning the magnetic properties with external stimuli like electric fields or light. This work provides valuable insights into the electronic structure and magnetic properties of this novel material, paving the way for future advancements in spintronics and materials science.

Nickel Intercalation into Niobium Diselenide Crystals

Scientists have demonstrated a method for growing high-quality crystals of nickel-intercalated niobium diselenide, a material with potential for hosting exotic electronic phases. Using the chemical vapor transport method, they carefully controlled the stoichiometry and employed iodine as a transport agent to grow hexagonal crystals. Detailed analysis using X-ray diffraction confirmed the crystal structure and composition, providing a foundation for further investigation. The team then employed a range of experimental techniques to characterize the material’s properties. Atomic force microscopy revealed the surface morphology of both pristine and nickel-intercalated crystals, while magnetic measurements demonstrated frustrated antiferromagnetic behavior below a specific temperature, indicating complex interactions between the magnetic moments within the material.

Angle-resolved photoemission spectroscopy provided insight into the electronic structure, revealing significant modifications to the electronic bands induced by the nickel intercalation. These experimental findings were corroborated by theoretical calculations, confirming a reconstruction of the Fermi surface, the boundary between occupied and unoccupied electronic states, driven by the intercalant. The results demonstrate that nickel intercalation not only suppresses the charge density wave and superconducting phases typically observed in pristine niobium diselenide but also induces magnetic frustration and alters the topology of the Fermi surface. This work positions nickel-intercalated niobium diselenide as a promising material for exploring correlated electron phases in low-dimensional systems, potentially leading to new functionalities and applications in future technologies.

Nickel Intercalation Induces Magnetic Frustration and Anisotropy

Researchers have investigated single crystals of nickel-intercalated niobium diselenide, revealing profound alterations to the material’s physical properties. Magnetic measurements demonstrate that the material exhibits magnetic frustration, a state where competing interactions prevent the establishment of a simple magnetic order. Below a specific temperature, the material displays antiferromagnetic ordering, where neighboring magnetic moments align in opposite directions, alongside a small net magnetic moment and magnetic hysteresis. The data suggests an inhomogeneous antiferromagnetic phase characterized by both magnetic disorder and frustration, with distinct Curie-Weiss temperatures indicating anisotropic spin interactions favoring a specific spin orientation.

Temperature-dependent resistivity measurements reveal complete suppression of both charge density waves and superconductivity, indicating a significant shift in the electronic ground state. Angle-resolved photoemission spectroscopy, conducted at a specific temperature, reveals a new electron pocket in the nickel-intercalated material, a feature absent in the pristine material. The electronic structure results demonstrate a shift in the van Hove singularity, a critical point in the electronic band structure, identified as the primary cause for the suppression of electronic orders. These findings align with theoretical predictions suggesting that nickel intercalation, coupled with cationic disorder, promotes frustrated antiferromagnetic stripe states, shifts the van Hove singularity, and reconstructs the Fermi surface in niobium diselenide. This work positions nickel-intercalated niobium diselenide within a magnetically frustrated, non-superconducting regime, highlighting how partial intercalation and disorder drive complex magnetic order and Fermi surface reconstruction in low-dimensional materials.

Nickel Intercalation Suppresses Superconductivity and Frustration

Scientists have investigated crystals of nickel niobium selenide, revealing substantial changes to the material’s properties following the introduction of nickel. Magnetic measurements demonstrate that the nickel-intercalated compound exhibits magnetic frustration, establishing antiferromagnetic ordering below a specific temperature, alongside a small net magnetic moment and magnetic hysteresis. The system displays distinct Curie-Weiss temperatures, indicating anisotropic spin interactions favoring a specific spin orientation. Notably, the introduction of nickel completely suppresses both charge density waves and superconductivity within the material, extending down to extremely low temperatures.

Angle-resolved photoemission spectroscopy revealed a new electron pocket within the nickel-intercalated compound, absent in the original material, and a shift in the van Hove singularity, which appears to be the primary cause of the suppression of electronic ordering. These findings align with theoretical predictions suggesting that nickel intercalation and resulting disorder promote frustrated antiferromagnetic states and reconstruct the material’s Fermi surface. The authors acknowledge that the level of nickel intercalation is not perfectly controlled, introducing some degree of disorder into the crystal structure. Future research could focus on achieving more precise control over the nickel content to further investigate the relationship between disorder, magnetic frustration, and the suppression of superconductivity. This work positions nickel niobium selenide as a magnetically frustrated, non-superconducting material, demonstrating a new pathway to engineer correlated electron phases in low-dimensional materials.