Low-temperature magnetic order rearrangement in the layered van der-Waals compound MnPS₃

Sayan Chaudhuri^1*, C. N. Kuo^2,3, Y. S. Chen¹, C. S. Lue^2,3, J. G. Lin^1,4

¹Center for Condensed Matter Science, National Taiwan University, Taipei city, Taiwan
²Department of Physics, National Cheng Kung University, Tainan, Taiwan
³Taiwan Consortium of Emergent Crystalline Materials, Ministry of Science and Technology, Taipei city, Taiwan
⁴Center of Atomic Initiatives for New Materials, National Taiwan University, Taipei city, Taiwan

* Presenter:Sayan Chaudhuri, email:csayan895@gmail.com

Transition-metal phosphotrichalcogenides, MPX₃ where M is a transition metal and X is a chalcogenide, form a large family of layered compounds with tremendous potential applications in the chemical, electrochemical and medical fields. The wide range of properties in these materials tunable by proper selection of M and X elements and layer numbers acquired immense research interest from a fundamental science point of view as well as for practical applications in spintronic devices, Lithium batteries, thermoelectrics etc. MnPS3₃ a member of this family has 2D Heisenberg antiferromagnetic (HAFM) structure with T_N at 78 K and transform to a XY-system below 55 K [1,2], although according to Mermin-Wagner (MW) theorem, magnetic ordering can not occur in 1D or 2D isotropic Heisenberg systems [3]. It is understood that MnPS₃ orders antiferromagnetically as a result of weak interlayer coupling and the transition to a XY system at low temperature occurs due to a strong in-plane anisotropy. Stabilizing the long-range magnetic ordering in two-dimensional (2D) materials is a challenge from both fundamental and application points of view. It is a result of delicate competition between thermal energy, magnetic exchange energy and spin frustration. In this work [4], we investigated the temperature and field effects on the HAFM spin structure of MnPS₃ using dc magnetic susceptibility and electron spin resonance (ESR) techniques with the applied field along two different directions, xy-plane(in-plane) and z-direction(out-of-plane). Clear development of three-step transitions was observed in the in-plane susceptibility for the first time. A low-temperature plateau from 78 to 38 K can be related to the HAFM ordering with spins pointing to the z-direction. Following, a sharp rising after the plateau suggests a transition into XY-system. The rising slope slows down at 30 K indicating a transition into another phase, possibly a vortex-antivortex state. By fitting the temperature-dependent in-plane ESR parameters with Berezinskii—Kosterlitz—Thouless (BKT) model in the range of 100 K – 300 K, we propose a spin 2D system with the vortex-antivortex structure below the HAFM transition. Susceptibility and ESR data show that the application of a high field along the z-direction destroys both the XY phase and the BKT transition, confirming the scenario of a topological phase transition at zero field. The field dependence of transition as seen in this work provides a route to tune different magnetic phases in 2D system for the future applications of spintronic devices.

References
[1] Y.-J. Sun, Q.-H. Tan, X.-L. Liu, Y.-F. Gao, and J. Zhang, Probing the Magnetic Ordering of Antiferromagnetic MnPS 3 by Raman Spectroscopy, J Phys Chem Lett 10, 3087 (2019).
[2] A. R. Wildes, H. M. Rønnow, B. Roessli, M. J. Harris, and K. W. Godfrey, Static and Dynamic Critical Properties of the Quasi-Two-Dimensional Antiferromagnet MnPS3, Phys Rev B 74, 094422 (2006).
[3] N. D. Mermin and H. Wagner, Absence of Ferromagnetism or Antiferromagnetism in One- or Two-Dimensional Isotropic Heisenberg Models, Phys Rev Lett 17, 1133 (1966).
[4] S. Chaudhuri, C. N. Kuo, Y. S. Chen, C. S. Lue, and J. G. Lin, Low-Temperature Magnetic Order Rearrangement in the Layered van Der Waals Compound MnPS3, Phys Rev B 106, 094416 (2022).

Keywords: magnetic vdW materials, spin dynamic, Electron spin resonance