Ferrimagnetic Order Induced by Disorder and Kitaev Interactions in a Cl-doped Kagome Spin Liquid Candidate

المفاهيم الأساسية

This study investigates the unusual coexistence of antiferromagnetic and ferromagnetic order in a Cl-doped kagome spin liquid candidate, attributing it to the interplay of alternating-bond hexagon (ABH) disorder and Kitaev interactions, which lead to the formation of ferromagnetic clusters within a larger antiferromagnetic order.

الملخص

Bibliographic Information:

Seth, A., Prestigiacomo, J. C., Xu, A., Zeng, Z., Ford, T. D., Shivaram, B.S., Li, S., Lee, P. A., & Kimchi, I. (2024). Disorder-induced spin-cluster ferrimagnetism in a doped kagome spin liquid candidate. arXiv:2411.11827v1 [cond-mat.str-el].

Research Objective:

This study aims to understand the unusual magnetic behavior observed in a Cl-doped kagome spin liquid candidate material, YCu3(OH)6[(ClxBr(1−x))3−y(OH)y], specifically the coexistence of antiferromagnetic and ferromagnetic order.

Methodology:

The researchers conducted magnetization measurements on single crystals of the material with varying Cl concentrations. They analyzed the temperature and field dependence of magnetization to identify the presence of ferromagnetic clusters within the antiferromagnetically ordered state. To explain their observations, they developed a theoretical model incorporating ABH disorder and Kitaev interactions.

Key Findings:

• The study reveals the emergence of ferromagnetic clusters below the antiferromagnetic ordering temperature (TN ≈ 14 K) in the Cl-doped kagome material.
• These clusters grow in size as the temperature decreases, eventually leading to bulk ferromagnetic order at a lower temperature (T* ≈ 7 K).
• Theoretical analysis suggests that ABH disorder, inherent to the material due to Cl doping, enhances short-range antiferromagnetic order.
• The presence of Kitaev interactions, arising from spin-orbit coupling, induces a ferromagnetic canting of spins within these short-range ordered clusters, leading to the formation of ferromagnetic moments.

Main Conclusions:

The coexistence of antiferromagnetic and ferromagnetic order in the Cl-doped kagome material is attributed to the interplay of ABH disorder and Kitaev interactions. This study highlights the significant role of disorder and anisotropic spin interactions in shaping the magnetic properties of kagome materials and provides insights into the complex magnetism observed in these systems.

Significance:

This research contributes to the understanding of quantum spin liquids and the factors influencing their magnetic behavior. The findings have implications for the development of materials with exotic magnetic properties and potential applications in spintronics and quantum computing.

Limitations and Future Research:

Further investigations are needed to explore the evolution of these ferromagnetic clusters with varying Cl concentrations and their potential role in the emergence of a possible Dirac quantum spin liquid state at lower Cl doping levels.

الإحصائيات

The antiferromagnetic ordering temperature (TN) is approximately 14 K.
A discernible change in the slope of magnetization occurs around 7 K.
The field-cooled and zero-field-cooled magnetization curves separate below approximately 10 K.
The estimated size of the ferromagnetic clusters at 7 K is a few dozen lattice sites.

اقتباسات

"This hysteresis is occurring for fields in the plane."
"The combination of experimental observation and theory suggests that kagome Kitaev-type interactions arise and are necessary ingredient, together with ABH disorder, for describing the magnetic fluctuations in this family of materials."

الرؤى الأساسية المستخلصة من

Disorder-induced spin-cluster ferrimagnetism in a doped kagome spin liquid candidate

by Arnab Seth, ... في arxiv.org 11-19-2024

https://arxiv.org/pdf/2411.11827.pdf

استفسارات أعمق

How does the interplay of ABH disorder and Kitaev interactions affect the potential for realizing a quantum spin liquid state in this material system at lower Cl doping levels?

The interplay of ABH disorder and Kitaev interactions presents both challenges and opportunities for realizing a quantum spin liquid (QSL) state in YCOB-Cl at lower Cl doping levels. Here's a breakdown:
Challenges:

Suppression of long-range order: While ABH disorder can enhance quantum fluctuations and promote short-range order, it can also hinder the development of the long-range entanglement necessary for a QSL. The formation of spin singlets on strong ABH bonds might compete with the formation of a spin liquid state.
Ferromagnetic cluster formation: Kitaev interactions, in conjunction with ABH disorder, can lead to the formation of ferromagnetic clusters. These clusters break time-reversal symmetry and can induce a mass term in the fermionic description of a Dirac spin liquid, ultimately driving the system away from the QSL state.
Opportunities:

Enhanced quantum fluctuations: The presence of ABH disorder introduces randomness in the exchange interactions, which can frustrate classical magnetic ordering and enhance quantum fluctuations. This enhanced quantum fluctuation regime is a crucial ingredient for stabilizing a QSL.
Tunability: The ability to tune the strength of both ABH disorder (through Cl/Br ratio) and Kitaev interactions (potentially through pressure or strain) provides a handle to explore different regions of the phase diagram and potentially access a QSL state.
Overall:
The key takeaway is that the interplay of ABH disorder and Kitaev interactions creates a complex landscape in the YCOB-Cl system. Navigating this landscape requires carefully balancing the competing tendencies towards both short-range order and enhanced quantum fluctuations. Further theoretical and experimental investigations are crucial to determine the optimal conditions for realizing a QSL state in this material system.

Could other forms of disorder, beyond ABH disorder, also contribute to the formation of ferromagnetic clusters in kagome materials?

Yes, besides ABH disorder, other forms of disorder can contribute to the formation of ferromagnetic clusters in kagome materials. Here are a few examples:

Bond randomness: Random variations in the strength of the exchange interactions, even without a specific pattern like ABH, can disrupt long-range order and favor the formation of domains with local ferromagnetic correlations.
Site dilution: Replacing magnetic ions with non-magnetic impurities introduces randomness in the spatial distribution of spins. This can lead to the formation of isolated clusters of spins that may exhibit ferromagnetic order.
Lattice distortions: Deviations from the ideal kagome geometry, such as bond angle variations or out-of-plane distortions, can modify the balance of exchange interactions and potentially favor ferromagnetic correlations within certain regions.
Further neighbor interactions: While the nearest-neighbor Heisenberg model is often used to describe kagome materials, longer-range interactions can play a significant role. The presence of even weak further neighbor interactions, particularly if they are ferromagnetic, can promote the formation of ferromagnetic clusters.
It's important to note that the specific type of disorder and its interplay with other interactions will determine the dominant mechanism for ferromagnetic cluster formation in a particular kagome material.

What are the potential implications of these findings for understanding the role of disorder and frustration in other frustrated magnetic systems beyond kagome lattices?

The findings in YCOB-Cl highlight the complex and often unexpected role of disorder and frustration in frustrated magnetic systems. Here are some broader implications:

Disorder as a tuning parameter: The study demonstrates how disorder can be used as a tuning parameter to explore different magnetic ground states. This is particularly relevant for frustrated systems where multiple competing phases might exist in close proximity.
Importance of anisotropic interactions: The observation of ferromagnetic clusters arising from the interplay of Kitaev interactions and ABH disorder emphasizes the importance of considering anisotropic, beyond-Heisenberg interactions in frustrated magnets. These interactions can significantly modify the magnetic ground state, even if they are relatively weak.
Relevance to other frustrated lattices: While the specific findings are for a kagome lattice, the underlying principles are relevant to other frustrated systems, such as triangular, honeycomb, and pyrochlore lattices. Disorder and anisotropic interactions can play a similarly crucial role in these systems.
Search for novel quantum states: The study underscores the potential of disordered and frustrated materials as platforms for discovering novel quantum states of matter. By carefully controlling and manipulating disorder, it might be possible to stabilize exotic phases like spin liquids or spin glasses.
Overall, the findings in YCOB-Cl provide valuable insights into the interplay of disorder, frustration, and anisotropic interactions in quantum magnetism. They highlight the need for a comprehensive approach that goes beyond simple models and considers the full complexity of real materials to understand and potentially harness the rich physics of frustrated magnets.