Spin-Phonon Coupling and Magnetic Transition in an Organic Molecule Intercalated Cr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub>.

Samanta, Sudeshna; Iturriaga, Hector; Mai, Thuc T; Biacchi, Adam J; Islam, Rajibul; Fullerton, John; Hight Walker, Angela R; Noufal, Mohamed et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

The manipulation of spin-phonon coupling in both formations and explorations of magnetism in two-dimensional van der Waals ferromagnetic semiconductors facilitates unprecedented prospects for spintronic devices. The interlayer engineering with spin-phonon coupling promises controllable magnetism via organic cation intercalation. Here, spectroscopic evidence reveals the intercalation effect on the intrinsic magnetic and electronic transitions in quasi-two-dimensional Cr<sub>2</sub>Ge<sub>2</sub>Te<sub>6</sub> using tetrabutyl ammonium (TBA<sup>+</sup>) as the intercalant. The temperature evolution of Raman modes, <i>E</i><sub>g</sub><sup>3</sup> and <i>A</i><sub>g</sub><sup>1</sup>, along with the magnetization measurements, unambiguously captures the enhancement of the ferromagnetic Curie temperature in the intercalated heterostructure. Moreover, the <i>E</i><sub>g</sub><sup>4</sup> mode highlights the increased effect of spin-phonon interaction in magnetic-order-induced lattice distortion. Combined with the first-principle calculations, we observed a substantial number of electrons transferred from TBA<sup>+</sup> to Cr through the interface. The interplay between spin-phonon coupling and magnetic ordering in van der Waals magnets appeals for further understanding of the manipulation of magnetism in layered heterostructures.