Spin Reorientation Driven Renormalization of Spin-Phonon Coupling in Fe$_4$GeTe$_2$
Abstract
Quasi-2D van der Waals ferromagnet FeGeTe, featuring the simultaneous presence of high Curie temperature ( K) and a spin-reorientation transition at K, is a rare system where strong interplay of spin dynamics, lattice vibrations, and electronic structure leads to a wide range of interesting phenomena. Here, we investigate the lattice response of exfoliated FeGeTe nanoflakes using temperature-dependent Raman spectroscopy. Polarization-resolved measurements reveal that, while one Raman mode exhibits a purely out-of-plane character, the rest display mixed symmetry, reflecting interlayer vibrational nonuniformity and symmetry-driven mode degeneracies. Below , phonons harden, and the linewidth narrows, consistent with reduced anharmonicity, while across the spin reorientation transition at they display anomalous softening, linewidth broadening, and a peak in lifetime, which are signatures of strengthened spin-phonon coupling. Complementary DFT+DMFT calculations and atomistic spin dynamical simulations reveal temperature-dependent spin excitations whose energies overlap with the Raman-active phonons, providing a natural route for the observed magnon-phonon interaction. Together, these insights establish FeGeTe as a versatile platform for exploring intertwined spin, lattice, and electronic degrees of freedom, with relevance for dynamic spintronic and magneto-optic functionalities near technologically meaningful temperatures.
Cite
@article{arxiv.2512.18544,
title = {Spin Reorientation Driven Renormalization of Spin-Phonon Coupling in Fe$_4$GeTe$_2$},
author = {Riju Pal and Md. Nur Hasan and Chumki Nayak and Mrinal Deka and Nastaran Salehi and Manuel Pereiro and Suchanda Mondal and Abhishek Misra and Achintya Singha and Prabhat Mandal and Debjani Karmakar and Atindra Nath Pal},
journal= {arXiv preprint arXiv:2512.18544},
year = {2025}
}
Comments
Main Text: 10 pages, 4 figures; Supplementary Information: 31 pages, 27 figures