Comprehensive Investigation of Magnetically Ordered States in Cr1/3NbS2 and Mn1/3NbS2 Using Nuclear Magnetic Resonance

Centrala begrepp

The study demonstrates that both Cr1/3NbS2 and Mn1/3NbS2 exhibit chiral helical magnetism, with detailed characterization of the magnetic phases using nuclear magnetic resonance techniques.

Sammanfattning

The content presents a comprehensive investigation of the magnetically ordered states in the transition metal dichalcogenide compounds Cr1/3NbS2 and Mn1/3NbS2 using nuclear magnetic resonance (NMR) techniques.

For Cr1/3NbS2, the 53Cr NMR data clearly identifies the compound as a textbook case of a chiral monoaxial helimagnet. The 53Cr NMR spectra show the signatures of the chiral soliton lattice (CSL), chiral conical phase (CCP), and forced ferromagnetic (FFM) phases as a function of applied magnetic field. The extracted conical angle θ(H) agrees well with mean-field theory predictions. The transition from the chiral helimagnetic (CHM) to paramagnetic phase is found to be of first-order.

The 55Mn NMR results for Mn1/3NbS2 are more complex due to higher structural disorder, but still confirm the presence of a CHM phase. The 55Mn spectra exhibit multiple broad components attributed to different local magnetic environments, likely arising from partial occupancy of the Mn 2b Wyckoff site. Despite the disorder, the analysis of spin-echo oscillations reveals the same type of interplay between quadrupolar and magnetic interactions as in the Cr compound, supporting the chiral conical model.

The DFT calculations provide further insights, predicting the EFG and hyperfine parameters in good agreement with the experimental observations. Overall, the study establishes that both Cr1/3NbS2 and Mn1/3NbS2 are chiral helical magnets, with the Cr compound representing a textbook case and the Mn compound exhibiting more complex magnetic behavior due to structural disorder.

Statistik

The critical field for the transition from the chiral conical phase to the forced ferromagnetic phase in Cr1/3NbS2 is μ0Hc = 1.35(1) T.
The critical field for the transition from the chiral conical phase to the forced ferromagnetic phase in Mn1/3NbS2 is μ0Hc = 5.0(5) T.
The Cr magnetic moment is estimated to be 2.6 μB at T = 0, H = 0, with a 13% reduction from the spin-only Cr3+ value of 3 μB.
The Nb magnetic moment is estimated to be 0.1-0.15 μB, opposite to that of Cr.

Citat

"The discovery of chiral helical magnetism (CHM) in Cr1/3NbS2 and the stabilization of a chiral soliton lattice (CSL) has attracted considerable interest in view of their potential technological applications."
"Despite the much larger density of specific defects in this second single crystal, we confirm the presence of a CHM phase in the Mn compound, characterized by a very large critical field for the forced ferromagnetic phase (≈5 T for the applied field along c)."

Viktiga insikter från

Disorder-resilient transition of helical to conical ground states in M$_{1/3}$NbS$_2$, M=Cr,Mn

by Mana... på arxiv.org 10-03-2024

https://arxiv.org/pdf/2410.01631.pdf

Djupare frågor

How do the magnetic properties of Cr1/3NbS2 and Mn1/3NbS2 compare to other transition metal dichalcogenide compounds with different intercalated magnetic ions?

The magnetic properties of Cr1/3NbS2 and Mn1/3NbS2 exhibit distinct characteristics that set them apart from other transition metal dichalcogenide (TMDC) compounds with different intercalated magnetic ions. Both Cr and Mn intercalated compounds demonstrate chiral helimagnetism (CHM), which is a result of the non-centrosymmetric crystal structure and the presence of Dzyaloshinskii-Moriya (DM) interactions. In contrast, TMDCs intercalated with other transition metals, such as V, Co, and Ni, typically exhibit different magnetic interactions, such as dominant antiferromagnetic exchange in the case of V and Co, or more complex magnetic orders due to competing interactions.
Cr1/3NbS2 is characterized by a well-defined chiral helimagnetic order, which transitions into various nonlinear magnetic structures under applied magnetic fields, such as chiral conical phases (CCP) and chiral soliton lattices (CSL). The presence of a strong ferromagnetic interaction in Cr1/3NbS2 leads to a relatively low critical field for the forced ferromagnetic phase. On the other hand, Mn1/3NbS2, despite having a higher density of structural defects, also exhibits CHM but with a significantly larger critical field for the forced ferromagnetic phase, indicating a more robust magnetic state under external perturbations.
In summary, while Cr1/3NbS2 and Mn1/3NbS2 share similarities in exhibiting chiral helimagnetism, their magnetic properties differ significantly from other TMDCs due to the unique interplay of magnetic interactions, structural characteristics, and the specific nature of the intercalated magnetic ions.

What are the potential technological applications of the chiral helical magnetism and topological soliton lattices observed in these materials?

The chiral helical magnetism (CHM) and topological soliton lattices (CSL) observed in Cr1/3NbS2 and Mn1/3NbS2 present several promising technological applications, particularly in the fields of spintronics, data storage, and quantum computing.

Spintronics: The unique magnetic properties of CHM allow for the manipulation of spin currents, which can be utilized in spintronic devices. These devices leverage the spin degree of freedom of electrons, potentially leading to faster and more energy-efficient data processing compared to traditional charge-based electronics.

Data Storage: The stability of topological soliton lattices can be harnessed for advanced data storage solutions. The ability to create and manipulate stable magnetic textures, such as solitons, could lead to high-density magnetic storage media that are less susceptible to thermal fluctuations, thereby enhancing data retention and reliability.

Quantum Computing: The nontrivial topological properties associated with CHM and CSL may be exploited in the development of topological qubits. These qubits are expected to be more robust against decoherence, making them ideal candidates for fault-tolerant quantum computing architectures.

Magnetic Sensors: The sensitivity of CHM to external magnetic fields can be utilized in the design of highly sensitive magnetic sensors. Such sensors could find applications in various fields, including medical imaging, geological exploration, and security systems.

In conclusion, the chiral helical magnetism and topological soliton lattices in Cr1/3NbS2 and Mn1/3NbS2 not only enhance our understanding of fundamental magnetic phenomena but also pave the way for innovative applications in next-generation technologies.

How could the structural disorder in Mn1/3NbS2 be further reduced or controlled to obtain a more homogeneous magnetic state?

To achieve a more homogeneous magnetic state in Mn1/3NbS2, it is crucial to address the structural disorder that arises from the intercalation of manganese ions. Several strategies can be employed to reduce or control this disorder:

Optimized Synthesis Techniques: Employing advanced synthesis methods, such as chemical vapor transport or hydrothermal synthesis, can help achieve better control over the stoichiometry and distribution of manganese ions within the crystal lattice. Fine-tuning the synthesis parameters, such as temperature, pressure, and precursor concentrations, can lead to improved crystallinity and reduced defect density.

Post-Synthesis Annealing: Subjecting the synthesized Mn1/3NbS2 to post-synthesis annealing treatments can help in healing structural defects and promoting the ordering of manganese ions. Controlled annealing in an inert atmosphere can facilitate the diffusion of manganese ions, leading to a more uniform distribution and reduced disorder.

Doping with Other Elements: Introducing small amounts of other transition metals or non-magnetic elements during the synthesis process can help stabilize the crystal structure and reduce disorder. This approach can also modify the magnetic interactions, potentially leading to enhanced magnetic properties.

Layered Structure Engineering: Engineering the layered structure of Mn1/3NbS2 by controlling the interlayer spacing through chemical intercalation or exfoliation techniques can help mitigate disorder. This can enhance the magnetic coupling between layers and promote a more homogeneous magnetic state.

Characterization and Feedback Loop: Implementing advanced characterization techniques, such as X-ray diffraction, scanning electron microscopy, and nuclear magnetic resonance, can provide insights into the structural and magnetic properties of Mn1/3NbS2. This information can be used to iteratively refine the synthesis process, leading to improved material quality.

By employing these strategies, it is possible to reduce structural disorder in Mn1/3NbS2, thereby enhancing its magnetic homogeneity and overall performance in potential applications.