Quasi-two-dimensional magnon identification in antiferromagneticFePS3via magneto-Raman spectroscopy

Abstract

Recently it was discovered that van der Waals-bonded magnetic materials retain long range magnetic ordering down to a single layer, opening many avenues in fundamental physics and potential applications of these fascinating materials. One such material is FePS3, a large spin (S=2) Mott insulator where the Fe atoms form a honeycomb lattice. In the bulk, FePS3 has been shown to be a quasi-two-dimensional-Ising antiferromagnet, with additional features in the Raman spectra emerging below the Néel temperature (TN) of approximately 120 K. Using magneto-Raman spectroscopy as an optical probe of magnetic structure, we show that one of these Raman-active modes in the magnetically ordered state is actually a magnon with a frequency of ≈3.7 THz (122 cm -1 ). Contrary to previous work, which interpreted this feature as a phonon, our Raman data shows the expected frequency shifting and splitting of the magnon as a function of temperature and magnetic field, respectively, where we determine the g-factor to be ≈2. In addition, the symmetry behavior of the magnon is studied by polarization-dependent Raman spectroscopy and explained using the magnetic point group of FePS3.

Distinct magneto-Raman signatures of spin-flip phase transitions in CrI3

“…Instead, the bulk magnon dispersion 35 at 5 K shows a low-energy magnon at Γ below 1 meV (8 cm −1 ), similar to what was measured by recent FM resonance experiments 36 , and magnons at the M point of the Brillouin zone at ≈9 meV and 15 meV. Furthermore, a recent Raman study of magnon excitations in FePS 3 showed it is possible for magnons to be present in both xx and xy in quasi-2D van der Waals magnets 20 . Thus, the B g nature of P 1 and P 2 is not conclusive evidence that they are magnons.…”

“…Raman spectroscopy is a powerful technique to study a variety of phenomena in 2D quantum materials, including effects of strain 16 , electron–phonon coupling 17 , phase transitions 18 , spin-phonon coupling 19 , and magnetic excitations 20 – 22 . In addition, the diffraction-limited spot size allows for the investigation of atomically thin samples and heterostructures using a non-contact probe.…”

van der Waals Magnets: Material Family, Detection and Modulation of Magnetism, and Perspective in Spintronics

“…For 2D MPQ 3 , plenty of works have focused on the indirect probe of magnetic order using Raman spectrum (Figure 2b-d), and the T N at 2D limit is obtained through analyzing the phonon anomaly or the peak splitting in the temperature-dependent Raman spectra. [55,58,62,63] Besides, the existence of magnon mode in 2D FePS 3 [63] and the long-distance magnon transport [64] in 2D MnPS 3 reveal their potentials in magnonics. Moreover, the theoretically predicted electrical control of valley polarization [65] in monolayer MnPSe 3 and the coupling of AFM order to valley order [66] in monolayer MnPS 3 make them possible for the applications in valleytronics.…”

Magneto-optics of layered two-dimensional semiconductors and heterostructures: Progress and prospects

“…CrBr3 exhibits ferromagnetism irrespective of its layer thickness 109 . Recently, magneto-Raman spectroscopy has been used to identify magnons in the layered antiferromagnets FePS3 293 , and MnPS3 294 . This approach could be extended to other layered magnetic materials to study magnetic excitations.…”