Investigation Of High-Frequency Electron Spin Dynamics In The Kagome-Lattice Ymn6sn6 Crystal

Kagome magnetic crystals received a great deal of research attention in the recent past for their intriguing magnetic properties. Recently, YMn6Sn6 (Y166) has shown to exhibit several nontrivial magnetic phases (such as the Distorted Spiral (DS) phase, Transverse Conical Spiral (TCS) phase, Fan-like (FL) phase and the Forced-Ferromagnetic (FF) phase) and complex magnetic interactions. In this work, we employed very high-frequency electron paramagnetic resonance (VHF-EPR) spectroscopy to investigate the local microscopic magnetic interactions of Mn ions in the Kagome Crystal Y166 to better understand the new observed magnetic phases. Particularly, we studied the temperature-dependent EPR behavior at variable very-high microwave frequency (ν = 120, 240, and 300 GHz). To broaden our knowledge and understanding of magnetic interactions, we also investigated the EPR spectral behavior above room temperature (5 K-350 K) on Y166 single crystals, where the magnetic field was applied in-plane (IP) and out-of-plane (OOP) orientations of the sample layers. In addition, we have performed EPR at room temperature (290 K) for v = 240 GHz to study the angular dependence of the resonance field, g-value, and linewidth as a function of angle of rotation θ (degrees). We find that the EPR linewidth of Y166 follows a (3cos2𝜃 − 1)2-like angular dependence whilst the g-value and resonance field follow a (3cos2𝜃 − 1)- like angular dependence which reveals the “W-shape and U-shape” of the linewidth and g-values, respectively. This behavior shows the presence of 2D spin correlations in Y166. This 2D character is responsible for spin fluctuations at higher temperatures. The temperature dependencies of the EPR signal behavior, signal width, and g-values were tracked to study the magnetic phase transitions in Y166 as a function of temperature (5 – 350 K).