Spin–phonon coupling in two-dimensional antiferromagnet Fe0.25TaSe2

The coupling between phonon and spin gives rise to intriguing phenomena, including phonon Hall effect, spin Seebeck effect, and charge density wave (CDW). Here, we investigate spin–phonon coupling and CDW transition in antiferromagnetic intercalated Fe0.25TaSe2 using Raman spectroscopy. Fe intercalation introduces a new phonon mode: the spin–phonon mode (SPM) with two components, SPM1 and SPM2, stemming from vibration of the intercalated Fe atoms. Below the Néel temperature of 130 K, the position ratio of SPM1 and SPM2 modes exhibits anomalous change, and the linewidth of SPM2 broadens suddenly, demonstrating spin–phonon coupling mediated by the antiferromagnetic ordering. The two-phonon mode observed in Fe0.25TaSe2 attenuates rapidly at 170 K, notably higher than the CDW transition temperature in TaSe2 (T = 100 K), indicating the Fe intercalation benefits the CDW transition. In addition, the twisting mode in Fe0.25TaSe2 is significantly enhanced compared to that in TaSe2 and exhibits an unusual redshift and significant broadening in linewidth with decreasing temperature, indicating the intercalated Fe plays a “bridging” role, which gradually weakens as the temperature decreases. These findings provide valuable insights into electron–phonon–spin coupling in low-dimensional magnetic materials.