Antiferromagnetic ordering in van der Waals 2D magnetic material MnPS ₃ probed by Raman spectroscopy

Abstract

Magnetic ordering in the two-dimensional limit has been one of the most important issues in condensed matter physics for the past several decades. The recent discovery of new magnetic van der Waals materials heralds a much-needed easy route for the studies of two-dimensional magnetism: the thickness dependence of the magnetic ordering has been examined by using Isingand XXZ-type magnetic van der Waals materials. Here, we investigated the magnetic ordering of MnPS3, a two-dimensional antiferromagnetic material of Heisenberg-type, by Raman spectroscopy from bulk all the way down to bilayer. The phonon modes that involve the vibrations of Mn ions exhibit characteristic changes as temperature gets lowered through the Néel temperature. In bulk MnPS3, the Raman peak at ~155 cm -1 becomes considerably broadened near the Néel temperature and upon further cooling is subsequently red-shifted. The measured peak positions and polarization dependences of the Raman spectra are in excellent agreement with our first-principles calculations. In few-layer MnPS3, the peak at ~155 cm -1 exhibits the characteristic red-shift at low temperatures down to the bilayer, indicating that the magnetic ordering is surprisingly stable at such a thin limit. Our work sheds light on the hitherto unexplored magnetic ordering in the Heisenberg-type antiferromagnetic systems in the atomic-layer limit. ∑ ∑where XY J and I J are spin-exchange energies on the basal plane and along the c-axis, respectively; j S α is the α (α = x, y, or z) component of total spin; and j and δ run through all lattice sites and all nearest-neighbors, respectively. All three fundamental models can be realized with the generic Hamiltonian: 0 XY J = for the Ising model, 0 I J = for the XY model, and XY I J J = for the Heisenberg model. According to the Mermin-Wagner theorem [4], no magnetic ordering is possible at any nonzero temperature in one-or two-dimensional isotropic Heisenberg models. On the other hand, 2D Ising systems can have magnetic ordering at finite temperatures according to Onsager [5].Transition metal phosphorus trisulfides (TMPS3) belong to a class of 2D van der Waals magnetic materials that can be exfoliated to atomically thin layers [6,7]. For transition metal elements like Fe, Ni, and Mn, the materials share the same crystal structures but the magnetic phase at low temperatures vary depending on the magnetic elements: Ising (Fe), XXZ (Ni), and

Biquadratic exchange interactions in two-dimensional magnets

“…This is also the case of Mn-based compounds, 2H-MnS 2 , 2H-MnSe 2 , MnPS 3 , MnPSe 3 ( Fig. 1d, e), which agreed with magnetometry measurements [20][21][22] . It is noteworthy that CuBr 3 and 2H-FeS 2 have substantially larger magnitudes of BQ exchange (Table 1) comparable to more complex materials, i.e., ferropnictides, where spin and electronic correlations are known to play a key role in the determination of their superconducting and strongly-correlated properties 23 .…”

Linear Magnetoelectric Phase in Ultrathin MnPS3 Probed by Optical Second Harmonic Generation

“…However spin Hall based measurements of D 2 in MnPS 3 put its value at merely 0.3 meV [35]. Since it is unlikely that D 2 is several times larger in ultrathin flakes compared to bulk crystals, especially given that Raman spectroscopy studies show no drastic changes in T AF or the phonon spectrum as a function of thickness [19], we rule out a non-collinear spin texture as the cause for ac mirror breaking. Instead, it is possible that the substrate induced strain tilts the easyaxis, causing the Néel ordered moments to rigidly cant out of the ac plane.…”

Magnetic-Field-Induced Quantum Phase Transitions in a van der Waals Magnet

“…Chromium triiodide (CrI 3 ) stands out among the large family of van der Waals (VDW) ferromagnets (FMs) investigated so far, because its isolated atomic crystal is one of the first two to realize two-dimensional (2D) ferromagnetic long-range order [1,2] in the monolayer limit, and more importantly, it is the first-ever interlayer antiferromagnetic (AFM) semiconductor [3][4][5][6] in its multilayer form. This phenomenon also makes CrI 3 distinct from the 2D intralayer AFMs [7][8][9]. From an application perspective, such unique magnetic properties of CrI 3 have already drawn enormous interest in developing novel device functionalities that are tunable by either magnetic [3][4][5][6] or electric [10][11][12] fields.…”