我們利用核磁共振技術來討論層狀反鐵磁材料MnPS3與FePS3之磁性特性，MnPS3與FePS3層與層間以凡德瓦力鍵結，為典型的準二維材料，被認為具有潛力於自旋電子學發展，做為未來的記憶體元件材料。於外加磁場垂直或平行樣品c*軸下，我們完成了31P 核磁共振量測，取得奈特位移並解析出超精細作用場，藉由比較這些結果幫助我們了解樣品內部的交互作用。核磁共振量測結果中，觀察到MnPS3與FePS3反鐵磁相變的臨界現象，分別良好地對應二維各向異性海森堡與二維易辛模型。此外，FePS3在外加磁場平行c*軸時，未能看到核磁共振譜線的分裂，說明此時FePS3的內磁場恰好平行於晶體的ab平面。

Summary
We report a 31P nuclear magnetic resonance (NMR) study of quasi-two-dimensional (2D) MnPS3 and FePS3 which have been identified as van der Waals antiferromagnets. We have carried out the Knight shift measurement with the external field perpendicular and parallel to the honeycomb layers. For each individual compound, the temperature dependence of the Knight shift exhibits pronounced difference with the crystalline orientation. The hyperfine field for each aligned direction in MnPS3 and FePS3 has been resolved. The comparison of these results would help understand the effect of the dipolar coupling on the observed Knight shifts. In addition, the splitting of the 31P NMR resonance line found in the antiferromagnetic ordered state reveals the existence of the static internal field on the phosphorous site which has been employed to characterize the magnetic phase transition. We further provided the strong evidence that the direction of the internal field is parallel to the ab plane in FePS3 since no splitting feature has been observed as the field is applied along the magnetic c* axis of FePS3.

[1] L. Wang, P. Hu, Y. Long, Z. Liu, and X. He, J. Mater. Chem. A 5, 22855 (2017).
[2] M. A. Susner, M. Chyasnavichyus, M. A. McGuire, P. Ganesh, and P. Maksymovych, Adv. Mater. 29, 1602852 (2017).
[3] F. Wang, T. A. Shifa, P. Yu, P. He, Y. Liu, F. Wang, Z. Wang, X. Zhan, X. Lou, F. Xia, and J. He, Adv. Funct. Mater. 28, 1802151 (2018).
[4] R. Brec, Solid State Ion. 22, 3 (1986).
[5] B. L. Chittari, Y. Park, D. Lee, M. Han, A. H. MacDonald, E. Hwang, and J. Jung, Phys. Rev. B 94, 184428 (2016).
[6] K. -Z. Du, X. -Z. Wang, Y. Liu, P. Hu, M. I. Utama, C. K. Gan, Q. Xiong, and C. Kloc, ACS Nano 10, 1738 (2016).
[7] Y. Ohno, and K. Hirama, J. Solid State Chem. 63, 258 (1986).
[8] V. Zhukov, S. Alvarez, and D. L. Novikov, J. Phys. Chem. Solids 57, 647 (1996).
[9] G. L. Flem, R. Brec, G. Ouvard, A. Louisy, and P. Segransan, J. Phys. Chem. Solids 43, 455 (1982).
[10] K. Okuda, K. Kurosawa, S. Saito, M. Honda, Z. Yu, and M. Date, J. Phys. Soc. Jpn. 55, 4456 (1986).
[11] P. A. Joy, and S. Vasudevan, Phys. Rev. B 46, 5425 (1992).
[12] A. McCreary, J. R. Simpson, T. T. Mai, R. D. McMichael, J. E. Douglas, N. Butch, C. Dennis, R. Valdés Aguilar, and A. R. Hight Walker, Phys. Rev. B 101, 064416 (2020).
[13] K. Kurosawa, S. Saito, and Y. Yamaguchi, J. Phys. Soc. Jpn. 52, 3919 (1983).
[14] A. R. Wildes, B. Roessli, B. Lebech, and K. W. Godfrey, J. Phys. Condens. Matter 10, 6417 (1998).
[15] K. C. Rule, G. J. McIntyre, S. J. Kennedy, and T. J. Hicks, Phys. Rev. B 76, 134402 (2007).
[16] E. Ressouche, M. Loire, V. Simonet, R. Ballou, A. Stunault, and A. Wildes, Phys. Rev. B 82, 100408 (2010).
[17] D. Lançon, H. C. Walker, E. Ressouche, B. Ouladdiaf, K. C. Rule, G. J. McIntyre, T. J. Hicks, H. M. Rønnow, and A. R. Wildes, Phys. Rev. B 94, 214407 (2016).
[18] P. Jernberg, S. Bjarman, and R. Wäppling, J. Magn. Magn. Mater. 46, 178 (1984).
[19] I. Chatterjee, Phys. Rev. B 51, 3937 (1995).
[20] Y. Takano, N. Arai, A. Arai, Y. Takahashi, K. Takase, and K. Sekizawa, J. Magn. Magn. Mater. 272-276, e593 (2004).
[21] A. R. Wildes, H. M. Rønnow, B. Roessli, M. J. Harris, and K. W. Godfrey, Phys. Rev. B 74, 094422 (2006).
[22] J. -U. Lee, S. Lee, J. H. Ryoo, S. Kang, T. Y. Kim, P. Kim, C. H. Park, J. G. Park, and H. Cheong, Nano. Lett. 16, 7433 (2016).
[23] T. Masubuchi, H. Hoya, T. Watanabe, Y. Takahashi, S. Ban, N. Ohkubo, K. Takase, and Y. Takano, J. Alloys Compd. 460, 668 (2008).
[24] C. Sourisseau, J. P. Forgerit, and Y. Mathey, J. Solid State Chem. 49, 134 (1983).
[25] I. Lagadic, P. G. Lacroix, and R. Clément, Chem. Mater. 9, 2004 (1997) .
[26] Y. Takano, A. Arai, Y. Takahashi, K. Takase, and K. Sekizawa, J. Appl. Phys. 93, 8197 (2003).
[27] A. van den Brink, G. Vermijs, A. Solignac, J. Koo, J. T. Kohlhepp, H. J. M. Swagten, and B. Koopmans, Nat. Commun. 7, 10854 (2016).
[28] Y. Wang, Z. Zhou, T. Wen, Y. Zhou, N. Li, F. Han, Y. Xiao, P. Chow, J. Sun, M. Pravica, A.L. Cornelius, W. Yang, and Y. Zhao, J. Am. Chem. Soc. 138, 15751 (2016).
[29] X. Wei, F. -G. Yan, C. Shen, Q. -S. Lv, and K. -Y. Wang, Chin. Phys. B 26, 038504 (2017).
[30] Z. Ur Rehman, Z. Muhammad, O. Adetunji Moses, W. Zhu, C. Wu, Q. He, M. Habib, and L. Song, Micromachines 9, 292 (2018).
[31] W. Xing, L. Qiu, X. Wang, Y. Yao, Y. Ma, R. Cai, S. Jia, X. C. Xie, and W. Han, Phys. Rev. X 9, 011026 (2019).
[32] N. M. Latiff, N. F. Rosli, C. C. Mayorga-Martinez, K. Szokolava, Z. Sofer, A. C. Fisher, and M. Pumera, FlatChem 18, 100134 (2019).
[33] D. Rakov, Y. Li, S. Niu, and P. Xu, J. Alloys Compd. 769, 532 (2018).
[34] W. Zhu, W. Gan, Z. Muhammad, C. Wang, C. Wu, H. Liu, D. Liu, K. Zhang, Q. He, H. Jiang, X. Zheng, Z. Sun, S. Chen, and L. Song, Chem. Commun. 54, 4481 (2018).
[35] T. Jungwirth, X. Marti, P. Wadley, and J. Wunderlich, Nat Nanotechnol. 11, 231 (2016).
[36] P. Wadley, J. Železný, C. Andrews, V. Hills, R. P. Campion, V. Novák, K. Olejník, F. Maccherozzi, S. S. Dhesi, S. Y. Martin, T. Wagner, J. Wunderlich, F. Freimuth, Y. Mokrousov, J. Kuneš, J. S. Chauhan, M. J. Grzybowski, A. W. Rushforth, K. W. Edmonds, B. L. Gallagher, and T. Jungwirth, Science 351, 587 (2016).
[37] V. Baltz, A. Manchon, M. Tsoi, T. Moriyama, T. Ono, and Y. Tserkovnyak, Rev. Mod. Phys. 90, 015005 (2018).
[38] G. C. Carter (1977), Metallic shifts in NMR (1ST ed), Pergamon Press.
[39] A. Abragam (1961), The Principles of Nuclear Magnetism (1st ed), Oxford University Press.
[40] Stephen Blundell (2001), Magnetism in Condensed Matter (1st ed), Oxford University Press.
[41] C. Berthier, Y. Chabre, and M. Minier, Solid State Commun. 28, 327 (1978).
[42] J. Ziolo, S. Torre, A. Rigamonti, and F. Borsa, J. Appl. Phys. 63, 3095 (1988).
[43] S. Torre, and J. Ziolo, Phys. Rev. B 39, 8915 (1989).
[44] R. Nath, Y. Furukawa, F. Borsa, E. E. Kaul, M. Baenitz, C. Geibel, and D. C. Johnston, Phys. Rev. B 80, 214430 (2009).
[45] A. P. Dioguardi, S. Selter, S. Aswartham, M. -I. Sturza, R. Murugesan, M. S. Eldeeb, L. Hozoi, B. Büchner, and H. -J. Grafe, arXiv:2004.05403.
[46] C. N. Kuo, and C. S. Lue, Phys. Rev. B 78, 212407 (2008).
[47] C. S. Lue, C. N. Kuo, T. H. Su, G. J. Redhammer, Phys. Rev. B 75, 014426 (2007).
[48] S. T. Bramwell, and P. C. W. Holdsworth, J. Phys. Condens. Matter. 5, L53 (1993).
[49] A. Pelissetto, and E. Vicari, Phys. Rep. 368, 549 (2002).