High-frequency electron spin resonance in Kagome-Lattice YMn₆Sn₆

Metallic Kagome magnets have received a great deal of research attention in recent years for their intriguing magnetic properties. Recently, YMn₆Sn₆(Y166), which belongs to this family of compounds, has been studied to show different magnetic phases including the distorted spiral (DS), transverse conical spiral (TCS), fan-like (FL) and the forced-ferromagnetic (FF) phases respectively. In this work, we employed very high-frequency electron spin resonance (VHF-ESR) spectroscopy to investigate the local microscopic magnetic interactions of Mn ions in Y166. Particularly, the temperature-dependent ESR behavior at variable very-high microwave frequency (ν= 120, 240, and 300 GHz) was studied. The ESR spectral behavior above room temperature (up to 350 K) on Y166 single crystals, where the magnetic field was applied in-plane and out-of-plane orientations of the sample layers was also investigated. A couple of non-trivial magnetic phases at different temperatures and frequencies, including the TCS, FL and FF phases were identified. The DS phase was not identified because our measurements were taken at fields higher than the fields (0-2 T) at which this phase occurs. In addition, angular dependence of the resonance field at room temperature (290 K) forv= 240 GHz follows a (3cos²θ- 1)- like angular dependence which reveals the 'U-shape' (from 0˚ to 180˚) of the resonance field. This behavior indicates the presence of 2D spin correlations in Y166. This work has implications in emerging applications such as high-frequency microwave and terahertz communications and spintronics.