Researchers Reveal Magnetic Exchange Interactions in Kagome Antiferromagnets FeGe and FeSn

Kagome magnets, with their distinctive arrangement of magnetic atoms, present a fascinating challenge for physicists seeking to understand exotic quantum states of matter, and recent research focuses on understanding the fundamental interactions driving their behaviour. Yitao Zheng, Yan Zhu, and Jun Hu investigate the magnetic exchange interactions within two such materials, iron germanium (FeGe) and iron tin (FeSn). Their work reveals a complex interplay between competing forces, where iron atoms within each layer favour alignment, but interactions between layers promote antiferromagnetism, a state where neighbouring magnetic moments oppose each other. Importantly, the team demonstrates that the strength of these interactions depends critically on the distance between iron atoms, suggesting a route to enhance magnetic properties through the application of external pressure, potentially leading to improved performance in future technologies.

Magnetic exchange interactions in kagome magnets exhibit rich features due to the interplay of charge, spin, orbital and lattice degrees of freedom, giving rise to a variety of exotic quantum states. These materials are of significant interest because their unique lattice geometry, a pattern of interconnected triangles, fosters unconventional magnetic behaviour and the potential for novel quantum phenomena. Through detailed calculations, researchers systematically investigate the magnetic exchange interactions in two representative kagome antiferromagnets, FeGe and FeSn, to understand the underlying mechanisms driving their magnetic properties. This work aims to provide a comprehensive understanding of these interactions, which is crucial for designing and discovering new quantum materials with tailored magnetic characteristics and functionalities.

The research investigates the magnetic properties of kagome antiferromagnets FeGe and FeSn, revealing that magnetic order arises from coupling between layers, with individual layers exhibiting ferromagnetic coupling. This ferromagnetic behaviour arises from a competition between direct interactions and RKKY interactions. FeGe exhibits a substantially higher temperature at which magnetic order is lost compared to FeSn, due to stronger direct interactions and weaker RKKY interactions. Interestingly, the calculations show a clear relationship between the distance between iron atoms and both the local spin moment and the nearest-neighbor exchange energy, suggesting a pathway to tune magnetic properties.

Kagome Lattices Reveal Complex Magnetic Interactions

This research provides a detailed investigation of the magnetic properties of FeGe and FeSn, materials possessing a distinctive kagome lattice structure. The study employs advanced calculations to determine the strength and nature of interactions between magnetic moments on neighboring iron atoms, and how these interactions lead to specific magnetic orderings. Researchers also explore how applying external strain influences the magnetic properties, including the strength of the magnetic moment and the interactions between atoms.

The calculations reveal several key findings regarding the exchange interactions between iron atoms, quantified by exchange constants that describe the strength and nature of the coupling. The study also investigates the contribution of the RKKY interaction, a long-range interaction that can influence the magnetic order. Importantly, the exchange energies are found to depend on the direction of the bonds between iron atoms.

The study also examines the electronic structure of the materials, calculating the band structure and the density of states, revealing the electronic contributions to the magnetic interactions and how strain affects the electronic structure. The calculations show that the spin moment of iron atoms is sensitive to applied strain.

The researchers estimate the temperature at which the materials lose their long-range magnetic order, known as the Néel temperature. The results demonstrate that applying strain can effectively tune the magnetic properties of both FeGe and FeSn, affecting the spin moment, exchange interactions, and potentially the magnetic ground state. A clear relationship is found between the distance between iron atoms and both the local spin moment and the nearest-neighbor exchange energy.

Kagome Antiferromagnets Tuned by Interlayer Coupling

This research systematically investigates the magnetic properties of FeGe and FeSn, materials possessing a distinctive kagome lattice structure. The study reveals that magnetic order in both materials arises from coupling between layers, with individual layers exhibiting ferromagnetic coupling driven by a competition between direct and RKKY interactions. FeGe demonstrates a substantially higher Néel temperature than FeSn due to stronger direct magnetic exchange interactions and weaker RKKY interactions. Importantly, the calculations show a clear relationship between the distance between iron atoms and both the local spin moment and the nearest-neighbor exchange energy, suggesting a pathway to tune magnetic properties.

The findings demonstrate that moderate compressive strain can significantly enhance the Néel temperature in both FeGe and FeSn, offering a practical method for engineering magnetic orders within these kagome magnets. While the materials are robust against moderate tensile strain, compression proves more effective in strengthening the antiferromagnetic state. Future work could explore complex interactions further to optimize strain-induced magnetic control. This research provides valuable insights into the fundamental magnetic behaviour of kagome materials and suggests potential strategies for tailoring their properties for technological applications.