Substitutional Fe Doping of WSe₂ Monolayers and Their Topological Hall Effect at Room-Temperature

The topological Hall effect (THE) is a significant transport property in magnetic materials, arising from spin texture irregularities. It has been widely studied in various magnetic systems[1, 2]. For example, skymions have been observed in chiral magnets such as Mn3Sn [3] and Mn3Ga [4], as well as in SrRuO3/SrTiO3 [5]and Pt/Tm3Fe5O12[6] heterostructures. Skyrmions are unique spin textures with potential applications in high-speed, low-energy consumption logic and memory devices [7]. Their formation is typically driven by the Dzyaloshinskii-Moriya interaction (DMI), a chiral exchange interaction encouraged by broken inversion symmetry [8]. This study presents the temperature-dependent ferromagnetic order in chemical vapor deposition (CVD)-grown Fe-doped WSe2 (Fe:WSe2) monolayers. Vibrating Sample Magnetometer (VSM) measurements reveal distinct magnetic hysteresis, affirming the ferromagnetic nature of Fe:WSe2, with sustained magnetic properties up to room temperature. Furthermore, distinct from the intrinsic anomalous Hall effect (AHE) in a ferromagnet, we find the transverse Hall resistivity of Fe:WSe2 displays two additional dip/peak features, consistent with the contribution of THE. The topological Hall effect is attributed to the magnetic skyrmions that emerge from the DMI at the Fe:WSe2 and Pt interface. THE in Fe:WSe2 monolayers highlight the potential for manipulating magnetic textures. The robustness of THE persistent up to room temperatures suggests the existence of stable induced skyrmion-like features. Complex spin textures from Fe doping, which are crucial for THE, are less affected by the thinness or interface irregularities that can weaken AHE. This research enhances our grasp of both ferromagnetism and the interplay between topological and anomalous Hall effects in 2D vdW magnetic systems, paving the way for creating scalable and integrated heterostructures into spintronic and non-volatile memory applications.<br/><br/>[1] G. Kimbell, C. Kim, W. Wu, M. Cuoco, and J. W. A. Robinson, “Challenges in identifying chiral spin textures via the topological Hall effect,” <i>Communications Materials</i>, <b>3</b> (1), 19, (2022).<br/>[2] H. Weng, R. Yu, X. Hu, X. Dai, and Z. Fang, “Quantum anomalous Hall effect and related topological electronic states,” <i>Advances in Physics</i>, <b>64</b> (3). Taylor and Francis Ltd., 227–282, 04-May-2015.<br/>[3] P. K. Rout, P. V. P. Madduri, S. K. Manna, and A. K. Nayak, “Field-induced topological Hall effect in the noncoplanar triangular antiferromagnetic geometry of Mn3Sn,” <i>Physical Review B</i>, <b>99</b> (9), (2019).<br/>[4] F. Hu, G. Xu, Y. You, Z. Zhang, Z. Xu, Y. Gong, E. Liu, H. Zhang, E. Liu, W. Wang, and F. Xu, “Tunable magnetic and transport properties of Mn3Ga thin films on Ta/Ru seed layer,” <i>Journal of Applied Physics</i>, <b>123</b> (10), (2018).<br/>[5] R. Zou, F. Zhan, B. Zheng, X. Wu, J. Fan, and R. Wang, “Intrinsic quantum anomalous Hall phase induced by proximity in the van der Waals heterostructure germanene/Cr 2 Ge 2 Te 6,” <i>Physical Review B</i>, <b>101</b> (16), 161108, (2020).<br/>[6] Z. Xu, Q. Liu, Y. Ji, X. Li, J. Li, J. Wang, and L. Chen, “Strain-Tunable Interfacial Dzyaloshinskii-Moriya Interaction and Spin-Hall Topological Hall Effect in Pt/Tm3Fe5O12Heterostructures,” <i>ACS Applied Materials and Interfaces</i>, <b>14</b> (14), 16791–16799, (2022).<br/>[7] A. J. Lee, A. S. Ahmed, J. Flores, S. Guo, B. Wang, N. Bagués, D. W. Mccomb, and F. Yang, “Probing the Source of the Interfacial Dzyaloshinskii-Moriya Interaction Responsible for the Topological Hall Effect in Metal/Tm3Fe5O12 Systems,” <i>Physical Review Letters</i>, <b>124</b> (10), (2020).<br/>[8] F. J. Dos Santos, M. Dos Santos Dias, and S. Lounis, “Nonreciprocity of spin waves in noncollinear magnets due to the Dzyaloshinskii-Moriya interaction,” <i>Physical Review B</i>, <b>102</b> (10), (2020).